text: /*! 
   * LESS - Leaner CSS v1.6.2 
   * http://lesscss.org 
   * 
   * Copyright (c) 2009-2014, Alexis Sellier <self@cloudhead.net> 
   * Licensed under the Apache v2 License. 
   * 
   */ 
  
   /** * @license Apache v2
   */ 
  
  
  
  (function (window, undefined) {//
  // Stub out `require` in the browser
  //
  function require(arg) {
      return window.less[arg.split('/')[1]];
  };
  
  
  if (typeof(window.less) === 'undefined' || typeof(window.less.nodeType) !== 'undefined') { window.less = {}; }
  less = window.less;
  tree = window.less.tree = {};
  less.mode = 'browser';
  
  var less, tree;
  
  // Node.js does not have a header file added which defines less
  if (less === undefined) {
      less = exports;
      tree = require('./tree');
      less.mode = 'node';
  }
  //
  // less.js - parser
  //
  //    A relatively straight-forward predictive parser.
  //    There is no tokenization/lexing stage, the input is parsed
  //    in one sweep.
  //
  //    To make the parser fast enough to run in the browser, several
  //    optimization had to be made:
  //
  //    - Matching and slicing on a huge input is often cause of slowdowns.
  //      The solution is to chunkify the input into smaller strings.
  //      The chunks are stored in the `chunks` var,
  //      `j` holds the current chunk index, and `currentPos` holds
  //      the index of the current chunk in relation to `input`.
  //      This gives us an almost 4x speed-up.
  //
  //    - In many cases, we don't need to match individual tokens;
  //      for example, if a value doesn't hold any variables, operations
  //      or dynamic references, the parser can effectively 'skip' it,
  //      treating it as a literal.
  //      An example would be '1px solid #000' - which evaluates to itself,
  //      we don't need to know what the individual components are.
  //      The drawback, of course is that you don't get the benefits of
  //      syntax-checking on the CSS. This gives us a 50% speed-up in the parser,
  //      and a smaller speed-up in the code-gen.
  //
  //
  //    Token matching is done with the `$` function, which either takes
  //    a terminal string or regexp, or a non-terminal function to call.
  //    It also takes care of moving all the indices forwards.
  //
  //
  less.Parser = function Parser(env) {
      var input,       // LeSS input string
          i,           // current index in `input`
          j,           // current chunk
          temp,        // temporarily holds a chunk's state, for backtracking
          memo,        // temporarily holds `i`, when backtracking
          furthest,    // furthest index the parser has gone to
          chunks,      // chunkified input
          current,     // current chunk
          currentPos,  // index of current chunk, in `input`
          parser,
          parsers,
          rootFilename = env && env.filename;
  
      // Top parser on an import tree must be sure there is one "env"
      // which will then be passed around by reference.
      if (!(env instanceof tree.parseEnv)) {
          env = new tree.parseEnv(env);
      }
  
      var imports = this.imports = {
          paths: env.paths || [],  // Search paths, when importing
          queue: [],               // Files which haven't been imported yet
          files: env.files,        // Holds the imported parse trees
          contents: env.contents,  // Holds the imported file contents
          contentsIgnoredChars: env.contentsIgnoredChars, // lines inserted, not in the original less
          mime:  env.mime,         // MIME type of .less files
          error: null,             // Error in parsing/evaluating an import
          push: function (path, currentFileInfo, importOptions, callback) {
              var parserImports = this;
              this.queue.push(path);
  
              var fileParsedFunc = function (e, root, fullPath) {
                  parserImports.queue.splice(parserImports.queue.indexOf(path), 1); // Remove the path from the queue
  
                  var importedPreviously = fullPath in parserImports.files || fullPath === rootFilename;
  
                  parserImports.files[fullPath] = root;                        // Store the root
  
                  if (e && !parserImports.error) { parserImports.error = e; }
  
                  callback(e, root, importedPreviously, fullPath);
              };
  
              if (less.Parser.importer) {
                  less.Parser.importer(path, currentFileInfo, fileParsedFunc, env);
              } else {
                  less.Parser.fileLoader(path, currentFileInfo, function(e, contents, fullPath, newFileInfo) {
                      if (e) {fileParsedFunc(e); return;}
  
                      var newEnv = new tree.parseEnv(env);
  
                      newEnv.currentFileInfo = newFileInfo;
                      newEnv.processImports = false;
                      newEnv.contents[fullPath] = contents;
  
                      if (currentFileInfo.reference || importOptions.reference) {
                          newFileInfo.reference = true;
                      }
  
                      if (importOptions.inline) {
                          fileParsedFunc(null, contents, fullPath);
                      } else {
                          new(less.Parser)(newEnv).parse(contents, function (e, root) {
                              fileParsedFunc(e, root, fullPath);
                          });
                      }
                  }, env);
              }
          }
      };
  
      function save()    { temp = current; memo = currentPos = i; }
      function restore() { current = temp; currentPos = i = memo; }
  
      function sync() {
          if (i > currentPos) {
              current = current.slice(i - currentPos);
              currentPos = i;
          }
      }
      function isWhitespace(str, pos) {
          var code = str.charCodeAt(pos | 0);
          return (code <= 32) && (code === 32 || code === 10 || code === 9);
      }
      //
      // Parse from a token, regexp or string, and move forward if match
      //
      function $(tok) {
          var tokType = typeof tok,
              match, length;
  
          // Either match a single character in the input,
          // or match a regexp in the current chunk (`current`).
          //
          if (tokType === "string") {
              if (input.charAt(i) !== tok) {
                  return null;
              }
              skipWhitespace(1);
              return tok;
          }
  
          // regexp
          sync ();
          if (! (match = tok.exec(current))) {
              return null;
          }
  
          length = match[0].length;
  
          // The match is confirmed, add the match length to `i`,
          // and consume any extra white-space characters (' ' || '\n')
          // which come after that. The reason for this is that LeSS's
          // grammar is mostly white-space insensitive.
          //
          skipWhitespace(length);
  
          if(typeof(match) === 'string') {
              return match;
          } else {
              return match.length === 1 ? match[0] : match;
          }
      }
  
      // Specialization of $(tok)
      function $re(tok) {
          if (i > currentPos) {
              current = current.slice(i - currentPos);
              currentPos = i;
          }
          var m = tok.exec(current);
          if (!m) {
              return null;
          }
  
          skipWhitespace(m[0].length);
          if(typeof m === "string") {
              return m;
          }
  
          return m.length === 1 ? m[0] : m;
      }
  
      var _$re = $re;
  
      // Specialization of $(tok)
      function $char(tok) {
          if (input.charAt(i) !== tok) {
              return null;
          }
          skipWhitespace(1);
          return tok;
      }
  
      function skipWhitespace(length) {
          var oldi = i, oldj = j,
              curr = i - currentPos,
              endIndex = i + current.length - curr,
              mem = (i += length),
              inp = input,
              c;
  
          for (; i < endIndex; i++) {
              c = inp.charCodeAt(i);
              if (c > 32) {
                  break;
              }
  
              if ((c !== 32) && (c !== 10) && (c !== 9) && (c !== 13)) {
                  break;
              }
           }
  
          current = current.slice(length + i - mem + curr);
          currentPos = i;
  
          if (!current.length && (j < chunks.length - 1)) {
              current = chunks[++j];
              skipWhitespace(0); // skip space at the beginning of a chunk
              return true; // things changed
          }
  
          return oldi !== i || oldj !== j;
      }
  
      function expect(arg, msg) {
          // some older browsers return typeof 'function' for RegExp
          var result = (Object.prototype.toString.call(arg) === '[object Function]') ? arg.call(parsers) : $(arg);
          if (result) {
              return result;
          }
          error(msg || (typeof(arg) === 'string' ? "expected '" + arg + "' got '" + input.charAt(i) + "'"
                                                 : "unexpected token"));
      }
  
      // Specialization of expect()
      function expectChar(arg, msg) {
          if (input.charAt(i) === arg) {
              skipWhitespace(1);
              return arg;
          }
          error(msg || "expected '" + arg + "' got '" + input.charAt(i) + "'");
      }
  
      function error(msg, type) {
          var e = new Error(msg);
          e.index = i;
          e.type = type || 'Syntax';
          throw e;
      }
  
      // Same as $(), but don't change the state of the parser,
      // just return the match.
      function peek(tok) {
          if (typeof(tok) === 'string') {
              return input.charAt(i) === tok;
          } else {
              return tok.test(current);
          }
      }
  
      // Specialization of peek()
      function peekChar(tok) {
          return input.charAt(i) === tok;
      }
  
  
      function getInput(e, env) {
          if (e.filename && env.currentFileInfo.filename && (e.filename !== env.currentFileInfo.filename)) {
              return parser.imports.contents[e.filename];
          } else {
              return input;
          }
      }
  
      function getLocation(index, inputStream) {
          var n = index + 1,
              line = null,
              column = -1;
  
          while (--n >= 0 && inputStream.charAt(n) !== '\n') {
              column++;
          }
  
          if (typeof index === 'number') {
              line = (inputStream.slice(0, index).match(/\n/g) || "").length;
          }
  
          return {
              line: line,
              column: column
          };
      }
  
      function getDebugInfo(index, inputStream, env) {
          var filename = env.currentFileInfo.filename;
          if(less.mode !== 'browser' && less.mode !== 'rhino') {
              filename = require('path').resolve(filename);
          }
  
          return {
              lineNumber: getLocation(index, inputStream).line + 1,
              fileName: filename
          };
      }
  
      function LessError(e, env) {
          var input = getInput(e, env),
              loc = getLocation(e.index, input),
              line = loc.line,
              col  = loc.column,
              callLine = e.call && getLocation(e.call, input).line,
              lines = input.split('\n');
  
          this.type = e.type || 'Syntax';
          this.message = e.message;
          this.filename = e.filename || env.currentFileInfo.filename;
          this.index = e.index;
          this.line = typeof(line) === 'number' ? line + 1 : null;
          this.callLine = callLine + 1;
          this.callExtract = lines[callLine];
          this.stack = e.stack;
          this.column = col;
          this.extract = [
              lines[line - 1],
              lines[line],
              lines[line + 1]
          ];
      }
  
      LessError.prototype = new Error();
      LessError.prototype.constructor = LessError;
  
      this.env = env = env || {};
  
      // The optimization level dictates the thoroughness of the parser,
      // the lower the number, the less nodes it will create in the tree.
      // This could matter for debugging, or if you want to access
      // the individual nodes in the tree.
      this.optimization = ('optimization' in this.env) ? this.env.optimization : 1;
  
      //
      // The Parser
      //
      parser = {
  
          imports: imports,
          //
          // Parse an input string into an abstract syntax tree,
          // @param str A string containing 'less' markup
          // @param callback call `callback` when done.
          // @param [additionalData] An optional map which can contains vars - a map (key, value) of variables to apply
          //
          parse: function (str, callback, additionalData) {
              var root, line, lines, error = null, globalVars, modifyVars, preText = "";
  
              i = j = currentPos = furthest = 0;
  
              globalVars = (additionalData && additionalData.globalVars) ? less.Parser.serializeVars(additionalData.globalVars) + '\n' : '';
              modifyVars = (additionalData && additionalData.modifyVars) ? '\n' + less.Parser.serializeVars(additionalData.modifyVars) : '';
  
              if (globalVars || (additionalData && additionalData.banner)) {
                  preText = ((additionalData && additionalData.banner) ? additionalData.banner : "") + globalVars;
                  parser.imports.contentsIgnoredChars[env.currentFileInfo.filename] = preText.length;
              }
  
              str = str.replace(/\r\n/g, '\n');
              // Remove potential UTF Byte Order Mark
              input = str = preText + str.replace(/^\uFEFF/, '') + modifyVars;
              parser.imports.contents[env.currentFileInfo.filename] = str;
  
              // Split the input into chunks.
              chunks = (function (input) {
                  var len = input.length, level = 0, parenLevel = 0,
                      lastOpening, lastOpeningParen, lastMultiComment, lastMultiCommentEndBrace,
                      chunks = [], emitFrom = 0,
                      parserCurrentIndex, currentChunkStartIndex, cc, cc2, matched;
  
                  function fail(msg, index) {
                      error = new(LessError)({
                          index: index || parserCurrentIndex,
                          type: 'Parse',
                          message: msg,
                          filename: env.currentFileInfo.filename
                      }, env);
                  }
  
                  function emitChunk(force) {
                      var len = parserCurrentIndex - emitFrom;
                      if (((len < 512) && !force) || !len) {
                          return;
                      }
                      chunks.push(input.slice(emitFrom, parserCurrentIndex + 1));
                      emitFrom = parserCurrentIndex + 1;
                  }
  
                  for (parserCurrentIndex = 0; parserCurrentIndex < len; parserCurrentIndex++) {
                      cc = input.charCodeAt(parserCurrentIndex);
                      if (((cc >= 97) && (cc <= 122)) || (cc < 34)) {
                          // a-z or whitespace
                          continue;
                      }
  
                      switch (cc) {
                          case 40:                        // (
                              parenLevel++; 
                              lastOpeningParen = parserCurrentIndex; 
                              continue;
                          case 41:                        // )
                              if (--parenLevel < 0) {
                                  return fail("missing opening `(`");
                              }
                              continue;
                          case 59:                        // ;
                              if (!parenLevel) { emitChunk(); }
                              continue;
                          case 123:                       // {
                              level++; 
                              lastOpening = parserCurrentIndex; 
                              continue;
                          case 125:                       // }
                              if (--level < 0) {
                                  return fail("missing opening `{`");
                              }
                              if (!level) { emitChunk(); }
                              continue;
                          case 92:                        // \
                              if (parserCurrentIndex < len - 1) { parserCurrentIndex++; continue; }
                              return fail("unescaped `\\`");
                          case 34:
                          case 39:
                          case 96:                        // ", ' and `
                              matched = 0;
                              currentChunkStartIndex = parserCurrentIndex;
                              for (parserCurrentIndex = parserCurrentIndex + 1; parserCurrentIndex < len; parserCurrentIndex++) {
                                  cc2 = input.charCodeAt(parserCurrentIndex);
                                  if (cc2 > 96) { continue; }
                                  if (cc2 == cc) { matched = 1; break; }
                                  if (cc2 == 92) {        // \
                                      if (parserCurrentIndex == len - 1) {
                                          return fail("unescaped `\\`");
                                      }
                                      parserCurrentIndex++;
                                  }
                              }
                              if (matched) { continue; }
                              return fail("unmatched `" + String.fromCharCode(cc) + "`", currentChunkStartIndex);
                          case 47:                        // /, check for comment
                              if (parenLevel || (parserCurrentIndex == len - 1)) { continue; }
                              cc2 = input.charCodeAt(parserCurrentIndex + 1);
                              if (cc2 == 47) {
                                  // //, find lnfeed
                                  for (parserCurrentIndex = parserCurrentIndex + 2; parserCurrentIndex < len; parserCurrentIndex++) {
                                      cc2 = input.charCodeAt(parserCurrentIndex);
                                      if ((cc2 <= 13) && ((cc2 == 10) || (cc2 == 13))) { break; }
                                  }
                              } else if (cc2 == 42) {
                                  // /*, find */
                                  lastMultiComment = currentChunkStartIndex = parserCurrentIndex;
                                  for (parserCurrentIndex = parserCurrentIndex + 2; parserCurrentIndex < len - 1; parserCurrentIndex++) {
                                      cc2 = input.charCodeAt(parserCurrentIndex);
                                      if (cc2 == 125) { lastMultiCommentEndBrace = parserCurrentIndex; }
                                      if (cc2 != 42) { continue; }
                                      if (input.charCodeAt(parserCurrentIndex + 1) == 47) { break; }
                                  }
                                  if (parserCurrentIndex == len - 1) {
                                      return fail("missing closing `*/`", currentChunkStartIndex);
                                  }
                                  parserCurrentIndex++;
                              }
                              continue;
                          case 42:                       // *, check for unmatched */
                              if ((parserCurrentIndex < len - 1) && (input.charCodeAt(parserCurrentIndex + 1) == 47)) {
                                  return fail("unmatched `/*`");
                              }
                              continue;
                      }
                  }
  
                  if (level !== 0) {
                      if ((lastMultiComment > lastOpening) && (lastMultiCommentEndBrace > lastMultiComment)) {
                          return fail("missing closing `}` or `*/`", lastOpening);
                      } else {
                          return fail("missing closing `}`", lastOpening);
                      }
                  } else if (parenLevel !== 0) {
                      return fail("missing closing `)`", lastOpeningParen);
                  }
  
                  emitChunk(true);
                  return chunks;
              })(str);
  
              if (error) {
                  return callback(new(LessError)(error, env));
              }
  
              current = chunks[0];
  
              // Start with the primary rule.
              // The whole syntax tree is held under a Ruleset node,
              // with the `root` property set to true, so no `{}` are
              // output. The callback is called when the input is parsed.
              try {
                  root = new(tree.Ruleset)(null, this.parsers.primary());
                  root.root = true;
                  root.firstRoot = true;
              } catch (e) {
                  return callback(new(LessError)(e, env));
              }
  
              root.toCSS = (function (evaluate) {
                  return function (options, variables) {
                      options = options || {};
                      var evaldRoot,
                          css,
                          evalEnv = new tree.evalEnv(options);
                          
                      //
                      // Allows setting variables with a hash, so:
                      //
                      //   `{ color: new(tree.Color)('#f01') }` will become:
                      //
                      //   new(tree.Rule)('@color',
                      //     new(tree.Value)([
                      //       new(tree.Expression)([
                      //         new(tree.Color)('#f01')
                      //       ])
                      //     ])
                      //   )
                      //
                      if (typeof(variables) === 'object' && !Array.isArray(variables)) {
                          variables = Object.keys(variables).map(function (k) {
                              var value = variables[k];
  
                              if (! (value instanceof tree.Value)) {
                                  if (! (value instanceof tree.Expression)) {
                                      value = new(tree.Expression)([value]);
                                  }
                                  value = new(tree.Value)([value]);
                              }
                              return new(tree.Rule)('@' + k, value, false, null, 0);
                          });
                          evalEnv.frames = [new(tree.Ruleset)(null, variables)];
                      }
  
                      try {
                          var preEvalVisitors = [],
                              visitors = [
                                  new(tree.joinSelectorVisitor)(),
                                  new(tree.processExtendsVisitor)(),
                                  new(tree.toCSSVisitor)({compress: Boolean(options.compress)})
                              ], i, root = this;
  
                          if (options.plugins) {
                              for(i =0; i < options.plugins.length; i++) {
                                  if (options.plugins[i].isPreEvalVisitor) {
                                      preEvalVisitors.push(options.plugins[i]);
                                  } else {
                                      if (options.plugins[i].isPreVisitor) {
                                          visitors.splice(0, 0, options.plugins[i]);
                                      } else {
                                          visitors.push(options.plugins[i]);
                                      }
                                  }
                              }
                          }
  
                          for(i = 0; i < preEvalVisitors.length; i++) {
                              preEvalVisitors[i].run(root);
                          }
  
                          evaldRoot = evaluate.call(root, evalEnv);
  
                          for(i = 0; i < visitors.length; i++) {
                              visitors[i].run(evaldRoot);
                          }
  
                          if (options.sourceMap) {
                              evaldRoot = new tree.sourceMapOutput(
                                  {
                                      contentsIgnoredCharsMap: parser.imports.contentsIgnoredChars,
                                      writeSourceMap: options.writeSourceMap,
                                      rootNode: evaldRoot,
                                      contentsMap: parser.imports.contents,
                                      sourceMapFilename: options.sourceMapFilename,
                                      sourceMapURL: options.sourceMapURL,
                                      outputFilename: options.sourceMapOutputFilename,
                                      sourceMapBasepath: options.sourceMapBasepath,
                                      sourceMapRootpath: options.sourceMapRootpath,
                                      outputSourceFiles: options.outputSourceFiles,
                                      sourceMapGenerator: options.sourceMapGenerator
                                  });
                          }
  
                          css = evaldRoot.toCSS({
                                  compress: Boolean(options.compress),
                                  dumpLineNumbers: env.dumpLineNumbers,
                                  strictUnits: Boolean(options.strictUnits),
                                  numPrecision: 8});
                      } catch (e) {
                          throw new(LessError)(e, env);
                      }
  
                      if (options.cleancss && less.mode === 'node') {
                          var CleanCSS = require('clean-css'),
                              cleancssOptions = options.cleancssOptions || {};
  
                          if (cleancssOptions.keepSpecialComments === undefined) {
                              cleancssOptions.keepSpecialComments = "*";
                          }
                          cleancssOptions.processImport = false;
                          cleancssOptions.noRebase = true;
                          if (cleancssOptions.noAdvanced === undefined) {
                              cleancssOptions.noAdvanced = true;
                          }
  
                          return new CleanCSS(cleancssOptions).minify(css);
                      } else if (options.compress) {
                          return css.replace(/(^(\s)+)|((\s)+$)/g, "");
                      } else {
                          return css;
                      }
                  };
              })(root.eval);
  
              // If `i` is smaller than the `input.length - 1`,
              // it means the parser wasn't able to parse the whole
              // string, so we've got a parsing error.
              //
              // We try to extract a \n delimited string,
              // showing the line where the parse error occured.
              // We split it up into two parts (the part which parsed,
              // and the part which didn't), so we can color them differently.
              if (i < input.length - 1) {
                  i = furthest;
                  var loc = getLocation(i, input);
                  lines = input.split('\n');
                  line = loc.line + 1;
  
                  error = {
                      type: "Parse",
                      message: "Unrecognised input",
                      index: i,
                      filename: env.currentFileInfo.filename,
                      line: line,
                      column: loc.column,
                      extract: [
                          lines[line - 2],
                          lines[line - 1],
                          lines[line]
                      ]
                  };
              }
  
              var finish = function (e) {
                  e = error || e || parser.imports.error;
  
                  if (e) {
                      if (!(e instanceof LessError)) {
                          e = new(LessError)(e, env);
                      }
  
                      return callback(e);
                  }
                  else {
                      return callback(null, root);
                  }
              };
  
              if (env.processImports !== false) {
                  new tree.importVisitor(this.imports, finish)
                      .run(root);
              } else {
                  return finish();
              }
          },
  
          //
          // Here in, the parsing rules/functions
          //
          // The basic structure of the syntax tree generated is as follows:
          //
          //   Ruleset ->  Rule -> Value -> Expression -> Entity
          //
          // Here's some LESS code:
          //
          //    .class {
          //      color: #fff;
          //      border: 1px solid #000;
          //      width: @w + 4px;
          //      > .child {...}
          //    }
          //
          // And here's what the parse tree might look like:
          //
          //     Ruleset (Selector '.class', [
          //         Rule ("color",  Value ([Expression [Color #fff]]))
          //         Rule ("border", Value ([Expression [Dimension 1px][Keyword "solid"][Color #000]]))
          //         Rule ("width",  Value ([Expression [Operation "+" [Variable "@w"][Dimension 4px]]]))
          //         Ruleset (Selector [Element '>', '.child'], [...])
          //     ])
          //
          //  In general, most rules will try to parse a token with the `$()` function, and if the return
          //  value is truly, will return a new node, of the relevant type. Sometimes, we need to check
          //  first, before parsing, that's when we use `peek()`.
          //
          parsers: parsers = {
              //
              // The `primary` rule is the *entry* and *exit* point of the parser.
              // The rules here can appear at any level of the parse tree.
              //
              // The recursive nature of the grammar is an interplay between the `block`
              // rule, which represents `{ ... }`, the `ruleset` rule, and this `primary` rule,
              // as represented by this simplified grammar:
              //
              //     primary  →  (ruleset | rule)+
              //     ruleset  →  selector+ block
              //     block    →  '{' primary '}'
              //
              // Only at one point is the primary rule not called from the
              // block rule: at the root level.
              //
              primary: function () {
                  var mixin = this.mixin, $re = _$re, root = [], node;
  
                  while (current)
                  {
                      node = this.extendRule() || mixin.definition() || this.rule() || this.ruleset() ||
                          mixin.call() || this.comment() || this.directive();
                      if (node) {
                          root.push(node);
                      } else {
                          if (!($re(/^[\s\n]+/) || $re(/^;+/))) {
                              break;
                          }
                      }
                  }
  
                  return root;
              },
  
              // We create a Comment node for CSS comments `/* */`,
              // but keep the LeSS comments `//` silent, by just skipping
              // over them.
              comment: function () {
                  var comment;
  
                  if (input.charAt(i) !== '/') { return; }
  
                  if (input.charAt(i + 1) === '/') {
                      return new(tree.Comment)($re(/^\/\/.*/), true, i, env.currentFileInfo);
                  }
                  comment = $re(/^\/\*(?:[^*]|\*+[^\/*])*\*+\/\n?/);
                  if (comment) {
                      return new(tree.Comment)(comment, false, i, env.currentFileInfo);
                  }
              },
  
              comments: function () {
                  var comment, comments = [];
  
                  while(true) {
                      comment = this.comment();
                      if (!comment) {
                          break;
                      }
                      comments.push(comment);
                  }
  
                  return comments;
              },
  
              //
              // Entities are tokens which can be found inside an Expression
              //
              entities: {
                  //
                  // A string, which supports escaping " and '
                  //
                  //     "milky way" 'he\'s the one!'
                  //
                  quoted: function () {
                      var str, j = i, e, index = i;
  
                      if (input.charAt(j) === '~') { j++; e = true; } // Escaped strings
                      if (input.charAt(j) !== '"' && input.charAt(j) !== "'") { return; }
  
                      if (e) { $char('~'); }
  
                      str = $re(/^"((?:[^"\\\r\n]|\\.)*)"|'((?:[^'\\\r\n]|\\.)*)'/);
                      if (str) {
                          return new(tree.Quoted)(str[0], str[1] || str[2], e, index, env.currentFileInfo);
                      }
                  },
  
                  //
                  // A catch-all word, such as:
                  //
                  //     black border-collapse
                  //
                  keyword: function () {
                      var k;
  
                      k = $re(/^[_A-Za-z-][_A-Za-z0-9-]*/);
                      if (k) {
                          var color = tree.Color.fromKeyword(k);
                          if (color) {
                              return color;
                          }
                          return new(tree.Keyword)(k);
                      }
                  },
  
                  //
                  // A function call
                  //
                  //     rgb(255, 0, 255)
                  //
                  // We also try to catch IE's `alpha()`, but let the `alpha` parser
                  // deal with the details.
                  //
                  // The arguments are parsed with the `entities.arguments` parser.
                  //
                  call: function () {
                      var name, nameLC, args, alpha_ret, index = i;
  
                      name = /^([\w-]+|%|progid:[\w\.]+)\(/.exec(current);
                      if (!name) { return; }
  
                      name = name[1];
                      nameLC = name.toLowerCase();
                      if (nameLC === 'url') {
                          return null;
                      }
  
                      i += name.length;
  
                      if (nameLC === 'alpha') {
                          alpha_ret = parsers.alpha();
                          if(typeof alpha_ret !== 'undefined') {
                              return alpha_ret;
                          }
                      }
  
                      $char('('); // Parse the '(' and consume whitespace.
  
                      args = this.arguments();
  
                      if (! $char(')')) {
                          return;
                      }
  
                      if (name) { return new(tree.Call)(name, args, index, env.currentFileInfo); }
                  },
                  arguments: function () {
                      var args = [], arg;
  
                      while (true) {
                          arg = this.assignment() || parsers.expression();
                          if (!arg) {
                              break;
                          }
                          args.push(arg);
                          if (! $char(',')) {
                              break;
                          }
                      }
                      return args;
                  },
                  literal: function () {
                      return this.dimension() ||
                             this.color() ||
                             this.quoted() ||
                             this.unicodeDescriptor();
                  },
  
                  // Assignments are argument entities for calls.
                  // They are present in ie filter properties as shown below.
                  //
                  //     filter: progid:DXImageTransform.Microsoft.Alpha( *opacity=50* )
                  //
  
                  assignment: function () {
                      var key, value;
                      key = $re(/^\w+(?=\s?=)/i);
                      if (!key) {
                          return;
                      }
                      if (!$char('=')) {
                          return;
                      }
                      value = parsers.entity();
                      if (value) {
                          return new(tree.Assignment)(key, value);
                      }
                  },
  
                  //
                  // Parse url() tokens
                  //
                  // We use a specific rule for urls, because they don't really behave like
                  // standard function calls. The difference is that the argument doesn't have
                  // to be enclosed within a string, so it can't be parsed as an Expression.
                  //
                  url: function () {
                      var value;
  
                      if (input.charAt(i) !== 'u' || !$re(/^url\(/)) {
                          return;
                      }
  
                      value = this.quoted() || this.variable() ||
                              $re(/^(?:(?:\\[\(\)'"])|[^\(\)'"])+/) || "";
  
                      expectChar(')');
  
                      return new(tree.URL)((value.value != null || value instanceof tree.Variable)
                                          ? value : new(tree.Anonymous)(value), env.currentFileInfo);
                  },
  
                  //
                  // A Variable entity, such as `@fink`, in
                  //
                  //     width: @fink + 2px
                  //
                  // We use a different parser for variable definitions,
                  // see `parsers.variable`.
                  //
                  variable: function () {
                      var name, index = i;
  
                      if (input.charAt(i) === '@' && (name = $re(/^@@?[\w-]+/))) {
                          return new(tree.Variable)(name, index, env.currentFileInfo);
                      }
                  },
  
                  // A variable entity useing the protective {} e.g. @{var}
                  variableCurly: function () {
                      var curly, index = i;
  
                      if (input.charAt(i) === '@' && (curly = $re(/^@\{([\w-]+)\}/))) {
                          return new(tree.Variable)("@" + curly[1], index, env.currentFileInfo);
                      }
                  },
  
                  //
                  // A Hexadecimal color
                  //
                  //     #4F3C2F
                  //
                  // `rgb` and `hsl` colors are parsed through the `entities.call` parser.
                  //
                  color: function () {
                      var rgb;
  
                      if (input.charAt(i) === '#' && (rgb = $re(/^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})/))) {
                          return new(tree.Color)(rgb[1]);
                      }
                  },
  
                  //
                  // A Dimension, that is, a number and a unit
                  //
                  //     0.5em 95%
                  //
                  dimension: function () {
                      var value, c = input.charCodeAt(i);
                      //Is the first char of the dimension 0-9, '.', '+' or '-'
                      if ((c > 57 || c < 43) || c === 47 || c == 44) {
                          return;
                      }
  
                      value = $re(/^([+-]?\d*\.?\d+)(%|[a-z]+)?/);
                      if (value) {
                          return new(tree.Dimension)(value[1], value[2]);
                      }
                  },
  
                  //
                  // A unicode descriptor, as is used in unicode-range
                  //
                  // U+0??  or U+00A1-00A9
                  //
                  unicodeDescriptor: function () {
                      var ud;
  
                      ud = $re(/^U\+[0-9a-fA-F?]+(\-[0-9a-fA-F?]+)?/);
                      if (ud) {
                          return new(tree.UnicodeDescriptor)(ud[0]);
                      }
                  },
  
                  //
                  // JavaScript code to be evaluated
                  //
                  //     `window.location.href`
                  //
                  javascript: function () {
                      var str, j = i, e;
  
                      if (input.charAt(j) === '~') { j++; e = true; } // Escaped strings
                      if (input.charAt(j) !== '`') { return; }
                      if (env.javascriptEnabled !== undefined && !env.javascriptEnabled) {
                          error("You are using JavaScript, which has been disabled.");
                      }
  
                      if (e) { $char('~'); }
  
                      str = $re(/^`([^`]*)`/);
                      if (str) {
                          return new(tree.JavaScript)(str[1], i, e);
                      }
                  }
              },
  
              //
              // The variable part of a variable definition. Used in the `rule` parser
              //
              //     @fink:
              //
              variable: function () {
                  var name;
  
                  if (input.charAt(i) === '@' && (name = $re(/^(@[\w-]+)\s*:/))) { return name[1]; }
              },
  
              //
              // extend syntax - used to extend selectors
              //
              extend: function(isRule) {
                  var elements, e, index = i, option, extendList, extend;
  
                  if (!(isRule ? $re(/^&:extend\(/) : $re(/^:extend\(/))) { return; }
  
                  do {
                      option = null;
                      elements = null;
                      while (! (option = $re(/^(all)(?=\s*(\)|,))/))) {
                          e = this.element();
                          if (!e) { break; }
                          if (elements) { elements.push(e); } else { elements = [ e ]; }
                      }
  
                      option = option && option[1];
  
                      extend = new(tree.Extend)(new(tree.Selector)(elements), option, index);
                      if (extendList) { extendList.push(extend); } else { extendList = [ extend ]; }
  
                  } while($char(","));
                  
                  expect(/^\)/);
  
                  if (isRule) {
                      expect(/^;/);
                  }
  
                  return extendList;
              },
  
              //
              // extendRule - used in a rule to extend all the parent selectors
              //
              extendRule: function() {
                  return this.extend(true);
              },
              
              //
              // Mixins
              //
              mixin: {
                  //
                  // A Mixin call, with an optional argument list
                  //
                  //     #mixins > .square(#fff);
                  //     .rounded(4px, black);
                  //     .button;
                  //
                  // The `while` loop is there because mixins can be
                  // namespaced, but we only support the child and descendant
                  // selector for now.
                  //
                  call: function () {
                      var s = input.charAt(i), important = false, index = i, elemIndex,
                          elements, elem, e, c, args;
  
                      if (s !== '.' && s !== '#') { return; }
  
                      save(); // stop us absorbing part of an invalid selector
  
                      while (true) {
                          elemIndex = i;
                          e = $re(/^[#.](?:[\w-]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+/);
                          if (!e) {
                              break;
                          }
                          elem = new(tree.Element)(c, e, elemIndex, env.currentFileInfo);
                          if (elements) { elements.push(elem); } else { elements = [ elem ]; }
                          c = $char('>');
                      }
  
                      if (elements) {
                          if ($char('(')) {
                              args = this.args(true).args;
                              expectChar(')');
                          }
  
                          if (parsers.important()) {
                              important = true;
                          }
  
                          if (parsers.end()) {
                              return new(tree.mixin.Call)(elements, args, index, env.currentFileInfo, important);
                          }
                      }
  
                      restore();
                  },
                  args: function (isCall) {
                      var parsers = parser.parsers, entities = parsers.entities,
                          returner = { args:null, variadic: false },
                          expressions = [], argsSemiColon = [], argsComma = [],
                          isSemiColonSeperated, expressionContainsNamed, name, nameLoop, value, arg;
  
                      while (true) {
                          if (isCall) {
                              arg = parsers.expression();
                          } else {
                              parsers.comments();
                              if (input.charAt(i) === '.' && $re(/^\.{3}/)) {
                                  returner.variadic = true;
                                  if ($char(";") && !isSemiColonSeperated) {
                                      isSemiColonSeperated = true;
                                  }
                                  (isSemiColonSeperated ? argsSemiColon : argsComma)
                                      .push({ variadic: true });
                                  break;
                              }
                              arg = entities.variable() || entities.literal() || entities.keyword();
                          }
  
                          if (!arg) {
                              break;
                          }
  
                          nameLoop = null;
                          if (arg.throwAwayComments) {
                              arg.throwAwayComments();
                          }
                          value = arg;
                          var val = null;
  
                          if (isCall) {
                              // Variable
                              if (arg.value.length == 1) {
                                  val = arg.value[0];
                              }
                          } else {
                              val = arg;
                          }
  
                          if (val && val instanceof tree.Variable) {
                              if ($char(':')) {
                                  if (expressions.length > 0) {
                                      if (isSemiColonSeperated) {
                                          error("Cannot mix ; and , as delimiter types");
                                      }
                                      expressionContainsNamed = true;
                                  }
                                  value = expect(parsers.expression);
                                  nameLoop = (name = val.name);
                              } else if (!isCall && $re(/^\.{3}/)) {
                                  returner.variadic = true;
                                  if ($char(";") && !isSemiColonSeperated) {
                                      isSemiColonSeperated = true;
                                  }
                                  (isSemiColonSeperated ? argsSemiColon : argsComma)
                                      .push({ name: arg.name, variadic: true });
                                  break;
                              } else if (!isCall) {
                                  name = nameLoop = val.name;
                                  value = null;
                              }
                          }
  
                          if (value) {
                              expressions.push(value);
                          }
  
                          argsComma.push({ name:nameLoop, value:value });
  
                          if ($char(',')) {
                              continue;
                          }
  
                          if ($char(';') || isSemiColonSeperated) {
  
                              if (expressionContainsNamed) {
                                  error("Cannot mix ; and , as delimiter types");
                              }
  
                              isSemiColonSeperated = true;
  
                              if (expressions.length > 1) {
                                  value = new(tree.Value)(expressions);
                              }
                              argsSemiColon.push({ name:name, value:value });
  
                              name = null;
                              expressions = [];
                              expressionContainsNamed = false;
                          }
                      }
  
                      returner.args = isSemiColonSeperated ? argsSemiColon : argsComma;
                      return returner;
                  },
                  //
                  // A Mixin definition, with a list of parameters
                  //
                  //     .rounded (@radius: 2px, @color) {
                  //        ...
                  //     }
                  //
                  // Until we have a finer grained state-machine, we have to
                  // do a look-ahead, to make sure we don't have a mixin call.
                  // See the `rule` function for more information.
                  //
                  // We start by matching `.rounded (`, and then proceed on to
                  // the argument list, which has optional default values.
                  // We store the parameters in `params`, with a `value` key,
                  // if there is a value, such as in the case of `@radius`.
                  //
                  // Once we've got our params list, and a closing `)`, we parse
                  // the `{...}` block.
                  //
                  definition: function () {
                      var name, params = [], match, ruleset, cond, variadic = false;
                      if ((input.charAt(i) !== '.' && input.charAt(i) !== '#') ||
                          peek(/^[^{]*\}/)) {
                          return;
                      }
  
                      save();
  
                      match = $re(/^([#.](?:[\w-]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+)\s*\(/);
                      if (match) {
                          name = match[1];
  
                          var argInfo = this.args(false);
                          params = argInfo.args;
                          variadic = argInfo.variadic;
  
                          // .mixincall("@{a}");
                          // looks a bit like a mixin definition.. so we have to be nice and restore
                          if (!$char(')')) {
                              furthest = i;
                              restore();
                          }
                          
                          parsers.comments();
  
                          if ($re(/^when/)) { // Guard
                              cond = expect(parsers.conditions, 'expected condition');
                          }
  
                          ruleset = parsers.block();
  
                          if (ruleset) {
                              return new(tree.mixin.Definition)(name, params, ruleset, cond, variadic);
                          } else {
                              restore();
                          }
                      }
                  }
              },
  
              //
              // Entities are the smallest recognized token,
              // and can be found inside a rule's value.
              //
              entity: function () {
                  var entities = this.entities;
  
                  return entities.literal() || entities.variable() || entities.url() ||
                         entities.call()    || entities.keyword()  || entities.javascript() ||
                         this.comment();
              },
  
              //
              // A Rule terminator. Note that we use `peek()` to check for '}',
              // because the `block` rule will be expecting it, but we still need to make sure
              // it's there, if ';' was ommitted.
              //
              end: function () {
                  return $char(';') || peekChar('}');
              },
  
              //
              // IE's alpha function
              //
              //     alpha(opacity=88)
              //
              alpha: function () {
                  var value;
  
                  if (! $re(/^\(opacity=/i)) { return; }
                  value = $re(/^\d+/) || this.entities.variable();
                  if (value) {
                      expectChar(')');
                      return new(tree.Alpha)(value);
                  }
              },
  
              //
              // A Selector Element
              //
              //     div
              //     + h1
              //     #socks
              //     input[type="text"]
              //
              // Elements are the building blocks for Selectors,
              // they are made out of a `Combinator` (see combinator rule),
              // and an element name, such as a tag a class, or `*`.
              //
              element: function () {
                  var e, c, v, index = i;
  
                  c = this.combinator();
  
                  e = $re(/^(?:\d+\.\d+|\d+)%/) || $re(/^(?:[.#]?|:*)(?:[\w-]|[^\x00-\x9f]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+/) ||
                      $char('*') || $char('&') || this.attribute() || $re(/^\([^()@]+\)/) || $re(/^[\.#](?=@)/) ||
                      this.entities.variableCurly();
  
                  if (! e) {
                      if ($char('(')) {
                          if ((v = this.selector()) && $char(')')) {
                              e = new(tree.Paren)(v);
                          }
                      }
                  }
  
                  if (e) { return new(tree.Element)(c, e, index, env.currentFileInfo); }
              },
  
              //
              // Combinators combine elements together, in a Selector.
              //
              // Because our parser isn't white-space sensitive, special care
              // has to be taken, when parsing the descendant combinator, ` `,
              // as it's an empty space. We have to check the previous character
              // in the input, to see if it's a ` ` character. More info on how
              // we deal with this in *combinator.js*.
              //
              combinator: function () {
                  var c = input.charAt(i);
                  
                  if (c === '>' || c === '+' || c === '~' || c === '|' || c === '^') {
                      i++;
                      if (input.charAt(i) === '^') {
                          c = '^^';
                          i++;
                      }
                      while (isWhitespace(input, i)) { i++; }
                      return new(tree.Combinator)(c);
                  } else if (isWhitespace(input, i - 1)) {
                      return new(tree.Combinator)(" ");
                  } else {
                      return new(tree.Combinator)(null);
                  }
              },
              //
              // A CSS selector (see selector below)
              // with less extensions e.g. the ability to extend and guard
              //
              lessSelector: function () {
                  return this.selector(true);
              },
              //
              // A CSS Selector
              //
              //     .class > div + h1
              //     li a:hover
              //
              // Selectors are made out of one or more Elements, see above.
              //
              selector: function (isLess) {
                  var index = i, $re = _$re, elements, extendList, c, e, extend, when, condition;
  
                  while ((isLess && (extend = this.extend())) || (isLess && (when = $re(/^when/))) || (e = this.element())) {
                      if (when) {
                          condition = expect(this.conditions, 'expected condition');
                      } else if (condition) {
                          error("CSS guard can only be used at the end of selector");
                      } else if (extend) {
                          if (extendList) { extendList.push(extend); } else { extendList = [ extend ]; }
                      } else {
                          if (extendList) { error("Extend can only be used at the end of selector"); }
                          c = input.charAt(i);
                          if (elements) { elements.push(e); } else { elements = [ e ]; }
                          e = null;
                      }
                      if (c === '{' || c === '}' || c === ';' || c === ',' || c === ')') {
                          break;
                      }
                  }
  
                  if (elements) { return new(tree.Selector)(elements, extendList, condition, index, env.currentFileInfo); }
                  if (extendList) { error("Extend must be used to extend a selector, it cannot be used on its own"); }
              },
              attribute: function () {
                  if (! $char('[')) { return; }
  
                  var entities = this.entities,
                      key, val, op;
  
                  if (!(key = entities.variableCurly())) {
                      key = expect(/^(?:[_A-Za-z0-9-\*]*\|)?(?:[_A-Za-z0-9-]|\\.)+/);
                  }
  
                  op = $re(/^[|~*$^]?=/);
                  if (op) {
                      val = entities.quoted() || $re(/^[0-9]+%/) || $re(/^[\w-]+/) || entities.variableCurly();
                  }
  
                  expectChar(']');
  
                  return new(tree.Attribute)(key, op, val);
              },
  
              //
              // The `block` rule is used by `ruleset` and `mixin.definition`.
              // It's a wrapper around the `primary` rule, with added `{}`.
              //
              block: function () {
                  var content;
                  if ($char('{') && (content = this.primary()) && $char('}')) {
                      return content;
                  }
              },
  
              //
              // div, .class, body > p {...}
              //
              ruleset: function () {
                  var selectors, s, rules, debugInfo;
                  
                  save();
  
                  if (env.dumpLineNumbers) {
                      debugInfo = getDebugInfo(i, input, env);
                  }
  
                  while (true) {
                      s = this.lessSelector();
                      if (!s) {
                          break;
                      }
                      if (selectors) { selectors.push(s); } else { selectors = [ s ]; }
                      this.comments();
                      if (s.condition && selectors.length > 1) {
                          error("Guards are only currently allowed on a single selector.");
                      }
                      if (! $char(',')) { break; }
                      if (s.condition) {
                          error("Guards are only currently allowed on a single selector.");
                      }
                      this.comments();
                  }
  
                  if (selectors && (rules = this.block())) {
                      var ruleset = new(tree.Ruleset)(selectors, rules, env.strictImports);
                      if (env.dumpLineNumbers) {
                          ruleset.debugInfo = debugInfo;
                      }
                      return ruleset;
                  } else {
                      // Backtrack
                      furthest = i;
                      restore();
                  }
              },
              rule: function (tryAnonymous) {
                  var name, value, c = input.charAt(i), important, merge = false;
                  save();
  
                  if (c === '.' || c === '#' || c === '&') { return; }
  
                  name = this.variable() || this.ruleProperty();
                  if (name) {
                      // prefer to try to parse first if its a variable or we are compressing
                      // but always fallback on the other one
                      value = !tryAnonymous && (env.compress || (name.charAt && (name.charAt(0) === '@'))) ?
                          (this.value() || this.anonymousValue()) :
                          (this.anonymousValue() || this.value());
  
                      important = this.important();
                      
                      // a name returned by this.ruleProperty() is always an array of the form:
                      // [string-1, ..., string-n, ""] or [string-1, ..., string-n, "+"]
                      // where each item is a tree.Keyword or tree.Variable
                      merge = name.pop && (name.pop().value === "+");
  
                      if (value && this.end()) {
                          return new (tree.Rule)(name, value, important, merge, memo, env.currentFileInfo);
                      } else {
                          furthest = i;
                          restore();
                          if (value && !tryAnonymous) {
                              return this.rule(true);
                          }
                      }
                  }
              },
              anonymousValue: function () {
                  var match;
                  match = /^([^@+\/'"*`(;{}-]*);/.exec(current);
                  if (match) {
                      i += match[0].length - 1;
                      return new(tree.Anonymous)(match[1]);
                  }
              },
  
              //
              // An @import directive
              //
              //     @import "lib";
              //
              // Depending on our environemnt, importing is done differently:
              // In the browser, it's an XHR request, in Node, it would be a
              // file-system operation. The function used for importing is
              // stored in `import`, which we pass to the Import constructor.
              //
              "import": function () {
                  var path, features, index = i;
  
                  save();
  
                  var dir = $re(/^@import?\s+/);
  
                  var options = (dir ? this.importOptions() : null) || {};
  
                  if (dir && (path = this.entities.quoted() || this.entities.url())) {
                      features = this.mediaFeatures();
                      if ($char(';')) {
                          features = features && new(tree.Value)(features);
                          return new(tree.Import)(path, features, options, index, env.currentFileInfo);
                      }
                  }
  
                  restore();
              },
  
              importOptions: function() {
                  var o, options = {}, optionName, value;
  
                  // list of options, surrounded by parens
                  if (! $char('(')) { return null; }
                  do {
                      o = this.importOption();
                      if (o) {
                          optionName = o;
                          value = true;
                          switch(optionName) {
                              case "css":
                                  optionName = "less";
                                  value = false;
                              break;
                              case "once":
                                  optionName = "multiple";
                                  value = false;
                              break;
                          }
                          options[optionName] = value;
                          if (! $char(',')) { break; }
                      }
                  } while (o);
                  expectChar(')');
                  return options;
              },
  
              importOption: function() {
                  var opt = $re(/^(less|css|multiple|once|inline|reference)/);
                  if (opt) {
                      return opt[1];
                  }
              },
  
              mediaFeature: function () {
                  var entities = this.entities, nodes = [], e, p;
                  do {
                      e = entities.keyword() || entities.variable();
                      if (e) {
                          nodes.push(e);
                      } else if ($char('(')) {
                          p = this.property();
                          e = this.value();
                          if ($char(')')) {
                              if (p && e) {
                                  nodes.push(new(tree.Paren)(new(tree.Rule)(p, e, null, null, i, env.currentFileInfo, true)));
                              } else if (e) {
                                  nodes.push(new(tree.Paren)(e));
                              } else {
                                  return null;
                              }
                          } else { return null; }
                      }
                  } while (e);
  
                  if (nodes.length > 0) {
                      return new(tree.Expression)(nodes);
                  }
              },
  
              mediaFeatures: function () {
                  var entities = this.entities, features = [], e;
                  do {
                      e = this.mediaFeature();
                      if (e) {
                          features.push(e);
                          if (! $char(',')) { break; }
                      } else {
                          e = entities.variable();
                          if (e) {
                              features.push(e);
                              if (! $char(',')) { break; }
                          }
                      }
                  } while (e);
  
                  return features.length > 0 ? features : null;
              },
  
              media: function () {
                  var features, rules, media, debugInfo;
  
                  if (env.dumpLineNumbers) {
                      debugInfo = getDebugInfo(i, input, env);
                  }
  
                  if ($re(/^@media/)) {
                      features = this.mediaFeatures();
  
                      rules = this.block();
                      if (rules) {
                          media = new(tree.Media)(rules, features, i, env.currentFileInfo);
                          if (env.dumpLineNumbers) {
                              media.debugInfo = debugInfo;
                          }
                          return media;
                      }
                  }
              },
  
              //
              // A CSS Directive
              //
              //     @charset "utf-8";
              //
              directive: function () {
                  var index = i, name, value, rules, nonVendorSpecificName,
                      hasBlock, hasIdentifier, hasExpression, identifier;
  
                  if (input.charAt(i) !== '@') { return; }
  
                  value = this['import']() || this.media();
                  if (value) {
                      return value;
                  }
  
                  save();
  
                  name = $re(/^@[a-z-]+/);
                  
                  if (!name) { return; }
  
                  nonVendorSpecificName = name;
                  if (name.charAt(1) == '-' && name.indexOf('-', 2) > 0) {
                      nonVendorSpecificName = "@" + name.slice(name.indexOf('-', 2) + 1);
                  }
  
                  switch(nonVendorSpecificName) {
                      case "@font-face":
                          hasBlock = true;
                          break;
                      case "@viewport":
                      case "@top-left":
                      case "@top-left-corner":
                      case "@top-center":
                      case "@top-right":
                      case "@top-right-corner":
                      case "@bottom-left":
                      case "@bottom-left-corner":
                      case "@bottom-center":
                      case "@bottom-right":
                      case "@bottom-right-corner":
                      case "@left-top":
                      case "@left-middle":
                      case "@left-bottom":
                      case "@right-top":
                      case "@right-middle":
                      case "@right-bottom":
                          hasBlock = true;
                          break;
                      case "@host":
                      case "@page":
                      case "@document":
                      case "@supports":
                      case "@keyframes":
                          hasBlock = true;
                          hasIdentifier = true;
                          break;
                      case "@namespace":
                          hasExpression = true;
                          break;
                  }
  
                  if (hasIdentifier) {
                      identifier = ($re(/^[^{]+/) || '').trim();
                      if (identifier) {
                          name += " " + identifier;
                      }
                  }
  
                  if (hasBlock) {
                      rules = this.block();
                      if (rules) {
                          return new(tree.Directive)(name, rules, index, env.currentFileInfo);
                      }
                  } else {
                      value = hasExpression ? this.expression() : this.entity();
                      if (value && $char(';')) {
                          var directive = new(tree.Directive)(name, value, index, env.currentFileInfo);
                          if (env.dumpLineNumbers) {
                              directive.debugInfo = getDebugInfo(i, input, env);
                          }
                          return directive;
                      }
                  }
  
                  restore();
              },
  
              //
              // A Value is a comma-delimited list of Expressions
              //
              //     font-family: Baskerville, Georgia, serif;
              //
              // In a Rule, a Value represents everything after the `:`,
              // and before the `;`.
              //
              value: function () {
                  var e, expressions = [];
  
                  do {
                      e = this.expression();
                      if (e) {
                          expressions.push(e);
                          if (! $char(',')) { break; }
                      }
                  } while(e);
  
                  if (expressions.length > 0) {
                      return new(tree.Value)(expressions);
                  }
              },
              important: function () {
                  if (input.charAt(i) === '!') {
                      return $re(/^! *important/);
                  }
              },
              sub: function () {
                  var a, e;
  
                  if ($char('(')) {
                      a = this.addition();
                      if (a) {
                          e = new(tree.Expression)([a]);
                          expectChar(')');
                          e.parens = true;
                          return e;
                      }
                  }
              },
              multiplication: function () {
                  var m, a, op, operation, isSpaced;
                  m = this.operand();
                  if (m) {
                      isSpaced = isWhitespace(input, i - 1);
                      while (true) {
                          if (peek(/^\/[*\/]/)) {
                              break;
                          }
                          op = $char('/') || $char('*');
  
                          if (!op) { break; }
  
                          a = this.operand();
  
                          if (!a) { break; }
  
                          m.parensInOp = true;
                          a.parensInOp = true;
                          operation = new(tree.Operation)(op, [operation || m, a], isSpaced);
                          isSpaced = isWhitespace(input, i - 1);
                      }
                      return operation || m;
                  }
              },
              addition: function () {
                  var m, a, op, operation, isSpaced;
                  m = this.multiplication();
                  if (m) {
                      isSpaced = isWhitespace(input, i - 1);
                      while (true) {
                          op = $re(/^[-+]\s+/) || (!isSpaced && ($char('+') || $char('-')));
                          if (!op) {
                              break;
                          }
                          a = this.multiplication();
                          if (!a) {
                              break;
                          }
                          
                          m.parensInOp = true;
                          a.parensInOp = true;
                          operation = new(tree.Operation)(op, [operation || m, a], isSpaced);
                          isSpaced = isWhitespace(input, i - 1);
                      }
                      return operation || m;
                  }
              },
              conditions: function () {
                  var a, b, index = i, condition;
  
                  a = this.condition();
                  if (a) {
                      while (true) {
                          if (!peek(/^,\s*(not\s*)?\(/) || !$char(',')) {
                              break;
                          }
                          b = this.condition();
                          if (!b) {
                              break;
                          }
                          condition = new(tree.Condition)('or', condition || a, b, index);
                      }
                      return condition || a;
                  }
              },
              condition: function () {
                  var entities = this.entities, index = i, negate = false,
                      a, b, c, op;
  
                  if ($re(/^not/)) { negate = true; }
                  expectChar('(');
                  a = this.addition() || entities.keyword() || entities.quoted();
                  if (a) {
                      op = $re(/^(?:>=|<=|=<|[<=>])/);
                      if (op) {
                          b = this.addition() || entities.keyword() || entities.quoted();
                          if (b) {
                              c = new(tree.Condition)(op, a, b, index, negate);
                          } else {
                              error('expected expression');
                          }
                      } else {
                          c = new(tree.Condition)('=', a, new(tree.Keyword)('true'), index, negate);
                      }
                      expectChar(')');
                      return $re(/^and/) ? new(tree.Condition)('and', c, this.condition()) : c;
                  }
              },
  
              //
              // An operand is anything that can be part of an operation,
              // such as a Color, or a Variable
              //
              operand: function () {
                  var entities = this.entities,
                      p = input.charAt(i + 1), negate;
  
                  if (input.charAt(i) === '-' && (p === '@' || p === '(')) { negate = $char('-'); }
                  var o = this.sub() || entities.dimension() ||
                          entities.color() || entities.variable() ||
                          entities.call();
  
                  if (negate) {
                      o.parensInOp = true;
                      o = new(tree.Negative)(o);
                  }
  
                  return o;
              },
  
              //
              // Expressions either represent mathematical operations,
              // or white-space delimited Entities.
              //
              //     1px solid black
              //     @var * 2
              //
              expression: function () {
                  var entities = [], e, delim;
  
                  do {
                      e = this.addition() || this.entity();
                      if (e) {
                          entities.push(e);
                          // operations do not allow keyword "/" dimension (e.g. small/20px) so we support that here
                          if (!peek(/^\/[\/*]/)) {
                              delim = $char('/');
                              if (delim) {
                                  entities.push(new(tree.Anonymous)(delim));
                              }
                          }
                      }
                  } while (e);
                  if (entities.length > 0) {
                      return new(tree.Expression)(entities);
                  }
              },
              property: function () {
                  var name = $re(/^(\*?-?[_a-zA-Z0-9-]+)\s*:/);
                  if (name) {
                      return name[1];
                  }
              },
              ruleProperty: function () {
                  var c = current, name = [], index = [], length = 0, s, k;
                  
                  function match(re) {
                      var a = re.exec(c);
                      if (a) {
                          index.push(i + length);
                          length += a[0].length;
                          c = c.slice(a[1].length);
                          return name.push(a[1]);
                      }
                  }
  
                  match(/^(\*?)/);
                  while (match(/^((?:[\w-]+)|(?:@\{[\w-]+\}))/)); // !
                  if ((name.length > 1) && match(/^\s*(\+?)\s*:/)) {
                      // at last, we have the complete match now. move forward, 
                      // convert name particles to tree objects and return:
                      skipWhitespace(length);
                      if (name[0] === '') {
                          name.shift();
                          index.shift();
                      }
                      for (k = 0; k < name.length; k++) {
                          s = name[k];
                          name[k] = (s.charAt(0) !== '@')
                              ? new(tree.Keyword)(s)
                              : new(tree.Variable)('@' + s.slice(2, -1), 
                                  index[k], env.currentFileInfo);
                      }
                      return name;
                  }
              }
          }
      };
      return parser;
  };
  less.Parser.serializeVars = function(vars) {
      var s = '';
  
      for (var name in vars) {
          if (Object.hasOwnProperty.call(vars, name)) {
              var value = vars[name];
              s += ((name[0] === '@') ? '' : '@') + name +': '+ value +
                      ((('' + value).slice(-1) === ';') ? '' : ';');
          }
      }
  
      return s;
  };
  
  (function (tree) {
  
  tree.functions = {
      rgb: function (r, g, b) {
          return this.rgba(r, g, b, 1.0);
      },
      rgba: function (r, g, b, a) {
          var rgb = [r, g, b].map(function (c) { return scaled(c, 255); });
          a = number(a);
          return new(tree.Color)(rgb, a);
      },
      hsl: function (h, s, l) {
          return this.hsla(h, s, l, 1.0);
      },
      hsla: function (h, s, l, a) {
          function hue(h) {
              h = h < 0 ? h + 1 : (h > 1 ? h - 1 : h);
              if      (h * 6 < 1) { return m1 + (m2 - m1) * h * 6; }
              else if (h * 2 < 1) { return m2; }
              else if (h * 3 < 2) { return m1 + (m2 - m1) * (2/3 - h) * 6; }
              else                { return m1; }
          }
  
          h = (number(h) % 360) / 360;
          s = clamp(number(s)); l = clamp(number(l)); a = clamp(number(a));
  
          var m2 = l <= 0.5 ? l * (s + 1) : l + s - l * s;
          var m1 = l * 2 - m2;
  
          return this.rgba(hue(h + 1/3) * 255,
                           hue(h)       * 255,
                           hue(h - 1/3) * 255,
                           a);
      },
  
      hsv: function(h, s, v) {
          return this.hsva(h, s, v, 1.0);
      },
  
      hsva: function(h, s, v, a) {
          h = ((number(h) % 360) / 360) * 360;
          s = number(s); v = number(v); a = number(a);
  
          var i, f;
          i = Math.floor((h / 60) % 6);
          f = (h / 60) - i;
  
          var vs = [v,
                    v * (1 - s),
                    v * (1 - f * s),
                    v * (1 - (1 - f) * s)];
          var perm = [[0, 3, 1],
                      [2, 0, 1],
                      [1, 0, 3],
                      [1, 2, 0],
                      [3, 1, 0],
                      [0, 1, 2]];
  
          return this.rgba(vs[perm[i][0]] * 255,
                           vs[perm[i][1]] * 255,
                           vs[perm[i][2]] * 255,
                           a);
      },
  
      hue: function (color) {
          return new(tree.Dimension)(Math.round(color.toHSL().h));
      },
      saturation: function (color) {
          return new(tree.Dimension)(Math.round(color.toHSL().s * 100), '%');
      },
      lightness: function (color) {
          return new(tree.Dimension)(Math.round(color.toHSL().l * 100), '%');
      },
      hsvhue: function(color) {
          return new(tree.Dimension)(Math.round(color.toHSV().h));
      },
      hsvsaturation: function (color) {
          return new(tree.Dimension)(Math.round(color.toHSV().s * 100), '%');
      },
      hsvvalue: function (color) {
          return new(tree.Dimension)(Math.round(color.toHSV().v * 100), '%');
      },
      red: function (color) {
          return new(tree.Dimension)(color.rgb[0]);
      },
      green: function (color) {
          return new(tree.Dimension)(color.rgb[1]);
      },
      blue: function (color) {
          return new(tree.Dimension)(color.rgb[2]);
      },
      alpha: function (color) {
          return new(tree.Dimension)(color.toHSL().a);
      },
      luma: function (color) {
          return new(tree.Dimension)(Math.round(color.luma() * color.alpha * 100), '%');
      },
      saturate: function (color, amount) {
          // filter: saturate(3.2);
          // should be kept as is, so check for color
          if (!color.rgb) {
              return null;
          }
          var hsl = color.toHSL();
  
          hsl.s += amount.value / 100;
          hsl.s = clamp(hsl.s);
          return hsla(hsl);
      },
      desaturate: function (color, amount) {
          var hsl = color.toHSL();
  
          hsl.s -= amount.value / 100;
          hsl.s = clamp(hsl.s);
          return hsla(hsl);
      },
      lighten: function (color, amount) {
          var hsl = color.toHSL();
  
          hsl.l += amount.value / 100;
          hsl.l = clamp(hsl.l);
          return hsla(hsl);
      },
      darken: function (color, amount) {
          var hsl = color.toHSL();
  
          hsl.l -= amount.value / 100;
          hsl.l = clamp(hsl.l);
          return hsla(hsl);
      },
      fadein: function (color, amount) {
          var hsl = color.toHSL();
  
          hsl.a += amount.value / 100;
          hsl.a = clamp(hsl.a);
          return hsla(hsl);
      },
      fadeout: function (color, amount) {
          var hsl = color.toHSL();
  
          hsl.a -= amount.value / 100;
          hsl.a = clamp(hsl.a);
          return hsla(hsl);
      },
      fade: function (color, amount) {
          var hsl = color.toHSL();
  
          hsl.a = amount.value / 100;
          hsl.a = clamp(hsl.a);
          return hsla(hsl);
      },
      spin: function (color, amount) {
          var hsl = color.toHSL();
          var hue = (hsl.h + amount.value) % 360;
  
          hsl.h = hue < 0 ? 360 + hue : hue;
  
          return hsla(hsl);
      },
      //
      // Copyright (c) 2006-2009 Hampton Catlin, Nathan Weizenbaum, and Chris Eppstein
      // http://sass-lang.com
      //
      mix: function (color1, color2, weight) {
          if (!weight) {
              weight = new(tree.Dimension)(50);
          }
          var p = weight.value / 100.0;
          var w = p * 2 - 1;
          var a = color1.toHSL().a - color2.toHSL().a;
  
          var w1 = (((w * a == -1) ? w : (w + a) / (1 + w * a)) + 1) / 2.0;
          var w2 = 1 - w1;
  
          var rgb = [color1.rgb[0] * w1 + color2.rgb[0] * w2,
                     color1.rgb[1] * w1 + color2.rgb[1] * w2,
                     color1.rgb[2] * w1 + color2.rgb[2] * w2];
  
          var alpha = color1.alpha * p + color2.alpha * (1 - p);
  
          return new(tree.Color)(rgb, alpha);
      },
      greyscale: function (color) {
          return this.desaturate(color, new(tree.Dimension)(100));
      },
      contrast: function (color, dark, light, threshold) {
          // filter: contrast(3.2);
          // should be kept as is, so check for color
          if (!color.rgb) {
              return null;
          }
          if (typeof light === 'undefined') {
              light = this.rgba(255, 255, 255, 1.0);
          }
          if (typeof dark === 'undefined') {
              dark = this.rgba(0, 0, 0, 1.0);
          }
          //Figure out which is actually light and dark!
          if (dark.luma() > light.luma()) {
              var t = light;
              light = dark;
              dark = t;
          }
          if (typeof threshold === 'undefined') {
              threshold = 0.43;
          } else {
              threshold = number(threshold);
          }
          if (color.luma() < threshold) {
              return light;
          } else {
              return dark;
          }
      },
      e: function (str) {
          return new(tree.Anonymous)(str instanceof tree.JavaScript ? str.evaluated : str);
      },
      escape: function (str) {
          return new(tree.Anonymous)(encodeURI(str.value).replace(/=/g, "%3D").replace(/:/g, "%3A").replace(/#/g, "%23").replace(/;/g, "%3B").replace(/\(/g, "%28").replace(/\)/g, "%29"));
      },
      '%': function (quoted /* arg, arg, ...*/) {
          var args = Array.prototype.slice.call(arguments, 1),
              str = quoted.value;
  
          for (var i = 0; i < args.length; i++) {
              /*jshint loopfunc:true */
              str = str.replace(/%[sda]/i, function(token) {
                  var value = token.match(/s/i) ? args[i].value : args[i].toCSS();
                  return token.match(/[A-Z]$/) ? encodeURIComponent(value) : value;
              });
          }
          str = str.replace(/%%/g, '%');
          return new(tree.Quoted)('"' + str + '"', str);
      },
      unit: function (val, unit) {
          if(!(val instanceof tree.Dimension)) {
              throw { type: "Argument", message: "the first argument to unit must be a number" + (val instanceof tree.Operation ? ". Have you forgotten parenthesis?" : "") };
          }
          return new(tree.Dimension)(val.value, unit ? unit.toCSS() : "");
      },
      convert: function (val, unit) {
          return val.convertTo(unit.value);
      },
      round: function (n, f) {
          var fraction = typeof(f) === "undefined" ? 0 : f.value;
          return _math(function(num) { return num.toFixed(fraction); }, null, n);
      },
      pi: function () {
          return new(tree.Dimension)(Math.PI);
      },
      mod: function(a, b) {
          return new(tree.Dimension)(a.value % b.value, a.unit);
      },
      pow: function(x, y) {
          if (typeof x === "number" && typeof y === "number") {
              x = new(tree.Dimension)(x);
              y = new(tree.Dimension)(y);
          } else if (!(x instanceof tree.Dimension) || !(y instanceof tree.Dimension)) {
              throw { type: "Argument", message: "arguments must be numbers" };
          }
  
          return new(tree.Dimension)(Math.pow(x.value, y.value), x.unit);
      },
      _minmax: function (isMin, args) {
          args = Array.prototype.slice.call(args);
          switch(args.length) {
          case 0: throw { type: "Argument", message: "one or more arguments required" };
          case 1: return args[0];
          }
          var i, j, current, currentUnified, referenceUnified, unit,
              order  = [], // elems only contains original argument values.
              values = {}; // key is the unit.toString() for unified tree.Dimension values,
                           // value is the index into the order array.
          for (i = 0; i < args.length; i++) {
              current = args[i];
              if (!(current instanceof tree.Dimension)) {
                  order.push(current);
                  continue;
              }
              currentUnified = current.unify();
              unit = currentUnified.unit.toString();
              j = values[unit];
              if (j === undefined) {
                  values[unit] = order.length;
                  order.push(current);
                  continue;
              }
              referenceUnified = order[j].unify();
              if ( isMin && currentUnified.value < referenceUnified.value ||
                  !isMin && currentUnified.value > referenceUnified.value) {
                  order[j] = current;
              }
          }
          if (order.length == 1) {
              return order[0];
          }
          args = order.map(function (a) { return a.toCSS(this.env); })
                      .join(this.env.compress ? "," : ", ");
          return new(tree.Anonymous)((isMin ? "min" : "max") + "(" + args + ")");
      },
      min: function () {
          return this._minmax(true, arguments);
      },
      max: function () {
          return this._minmax(false, arguments);
      },
      argb: function (color) {
          return new(tree.Anonymous)(color.toARGB());
      },
      percentage: function (n) {
          return new(tree.Dimension)(n.value * 100, '%');
      },
      color: function (n) {
          if (n instanceof tree.Quoted) {
              var colorCandidate = n.value,
                  returnColor;
              returnColor = tree.Color.fromKeyword(colorCandidate);
              if (returnColor) {
                  return returnColor;
              }
              if (/^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})/.test(colorCandidate)) {
                  return new(tree.Color)(colorCandidate.slice(1));
              }
              throw { type: "Argument", message: "argument must be a color keyword or 3/6 digit hex e.g. #FFF" };
          } else {
              throw { type: "Argument", message: "argument must be a string" };
          }
      },
      iscolor: function (n) {
          return this._isa(n, tree.Color);
      },
      isnumber: function (n) {
          return this._isa(n, tree.Dimension);
      },
      isstring: function (n) {
          return this._isa(n, tree.Quoted);
      },
      iskeyword: function (n) {
          return this._isa(n, tree.Keyword);
      },
      isurl: function (n) {
          return this._isa(n, tree.URL);
      },
      ispixel: function (n) {
          return this.isunit(n, 'px');
      },
      ispercentage: function (n) {
          return this.isunit(n, '%');
      },
      isem: function (n) {
          return this.isunit(n, 'em');
      },
      isunit: function (n, unit) {
          return (n instanceof tree.Dimension) && n.unit.is(unit.value || unit) ? tree.True : tree.False;
      },
      _isa: function (n, Type) {
          return (n instanceof Type) ? tree.True : tree.False;
      },
      tint: function(color, amount) {
          return this.mix(this.rgb(255,255,255), color, amount);
      },
      shade: function(color, amount) {
          return this.mix(this.rgb(0, 0, 0), color, amount);
      },   
      extract: function(values, index) {
          index = index.value - 1; // (1-based index)       
          // handle non-array values as an array of length 1
          // return 'undefined' if index is invalid
          return Array.isArray(values.value) 
              ? values.value[index] : Array(values)[index];
      },
      length: function(values) {
          var n = Array.isArray(values.value) ? values.value.length : 1;
          return new tree.Dimension(n);
      },
  
      "data-uri": function(mimetypeNode, filePathNode) {
  
          if (typeof window !== 'undefined') {
              return new tree.URL(filePathNode || mimetypeNode, this.currentFileInfo).eval(this.env);
          }
  
          var mimetype = mimetypeNode.value;
          var filePath = (filePathNode && filePathNode.value);
  
          var fs = require('fs'),
              path = require('path'),
              useBase64 = false;
  
          if (arguments.length < 2) {
              filePath = mimetype;
          }
  
          if (this.env.isPathRelative(filePath)) {
              if (this.currentFileInfo.relativeUrls) {
                  filePath = path.join(this.currentFileInfo.currentDirectory, filePath);
              } else {
                  filePath = path.join(this.currentFileInfo.entryPath, filePath);
              }
          }
  
          // detect the mimetype if not given
          if (arguments.length < 2) {
              var mime;
              try {
                  mime = require('mime');
              } catch (ex) {
                  mime = tree._mime;
              }
  
              mimetype = mime.lookup(filePath);
  
              // use base 64 unless it's an ASCII or UTF-8 format
              var charset = mime.charsets.lookup(mimetype);
              useBase64 = ['US-ASCII', 'UTF-8'].indexOf(charset) < 0;
              if (useBase64) { mimetype += ';base64'; }
          }
          else {
              useBase64 = /;base64$/.test(mimetype);
          }
  
          var buf = fs.readFileSync(filePath);
  
          // IE8 cannot handle a data-uri larger than 32KB. If this is exceeded
          // and the --ieCompat flag is enabled, return a normal url() instead.
          var DATA_URI_MAX_KB = 32,
              fileSizeInKB = parseInt((buf.length / 1024), 10);
          if (fileSizeInKB >= DATA_URI_MAX_KB) {
  
              if (this.env.ieCompat !== false) {
                  if (!this.env.silent) {
                      console.warn("Skipped data-uri embedding of %s because its size (%dKB) exceeds IE8-safe %dKB!", filePath, fileSizeInKB, DATA_URI_MAX_KB);
                  }
  
                  return new tree.URL(filePathNode || mimetypeNode, this.currentFileInfo).eval(this.env);
              }
          }
  
          buf = useBase64 ? buf.toString('base64')
                          : encodeURIComponent(buf);
  
          var uri = "\"data:" + mimetype + ',' + buf + "\"";
          return new(tree.URL)(new(tree.Anonymous)(uri));
      },
  
      "svg-gradient": function(direction) {
  
          function throwArgumentDescriptor() {
              throw { type: "Argument", message: "svg-gradient expects direction, start_color [start_position], [color position,]..., end_color [end_position]" };
          }
  
          if (arguments.length < 3) {
              throwArgumentDescriptor();
          }
          var stops = Array.prototype.slice.call(arguments, 1),
              gradientDirectionSvg,
              gradientType = "linear",
              rectangleDimension = 'x="0" y="0" width="1" height="1"',
              useBase64 = true,
              renderEnv = {compress: false},
              returner,
              directionValue = direction.toCSS(renderEnv),
              i, color, position, positionValue, alpha;
  
          switch (directionValue) {
              case "to bottom":
                  gradientDirectionSvg = 'x1="0%" y1="0%" x2="0%" y2="100%"';
                  break;
              case "to right":
                  gradientDirectionSvg = 'x1="0%" y1="0%" x2="100%" y2="0%"';
                  break;
              case "to bottom right":
                  gradientDirectionSvg = 'x1="0%" y1="0%" x2="100%" y2="100%"';
                  break;
              case "to top right":
                  gradientDirectionSvg = 'x1="0%" y1="100%" x2="100%" y2="0%"';
                  break;
              case "ellipse":
              case "ellipse at center":
                  gradientType = "radial";
                  gradientDirectionSvg = 'cx="50%" cy="50%" r="75%"';
                  rectangleDimension = 'x="-50" y="-50" width="101" height="101"';
                  break;
              default:
                  throw { type: "Argument", message: "svg-gradient direction must be 'to bottom', 'to right', 'to bottom right', 'to top right' or 'ellipse at center'" };
          }
          returner = '<?xml version="1.0" ?>' +
              '<svg xmlns="http://www.w3.org/2000/svg" version="1.1" width="100%" height="100%" viewBox="0 0 1 1" preserveAspectRatio="none">' +
              '<' + gradientType + 'Gradient id="gradient" gradientUnits="userSpaceOnUse" ' + gradientDirectionSvg + '>';
  
          for (i = 0; i < stops.length; i+= 1) {
              if (stops[i].value) {
                  color = stops[i].value[0];
                  position = stops[i].value[1];
              } else {
                  color = stops[i];
                  position = undefined;
              }
  
              if (!(color instanceof tree.Color) || (!((i === 0 || i+1 === stops.length) && position === undefined) && !(position instanceof tree.Dimension))) {
                  throwArgumentDescriptor();
              }
              positionValue = position ? position.toCSS(renderEnv) : i === 0 ? "0%" : "100%";
              alpha = color.alpha;
              returner += '<stop offset="' + positionValue + '" stop-color="' + color.toRGB() + '"' + (alpha < 1 ? ' stop-opacity="' + alpha + '"' : '') + '/>';
          }
          returner += '</' + gradientType + 'Gradient>' +
                      '<rect ' + rectangleDimension + ' fill="url(#gradient)" /></svg>';
  
          if (useBase64) {
              try {
                  returner = require('./encoder').encodeBase64(returner); // TODO browser implementation
              } catch(e) {
                  useBase64 = false;
              }
          }
  
          returner = "'data:image/svg+xml" + (useBase64 ? ";base64" : "") + "," + returner + "'";
          return new(tree.URL)(new(tree.Anonymous)(returner));
      }
  };
  
  // these static methods are used as a fallback when the optional 'mime' dependency is missing
  tree._mime = {
      // this map is intentionally incomplete
      // if you want more, install 'mime' dep
      _types: {
          '.htm' : 'text/html',
          '.html': 'text/html',
          '.gif' : 'image/gif',
          '.jpg' : 'image/jpeg',
          '.jpeg': 'image/jpeg',
          '.png' : 'image/png'
      },
      lookup: function (filepath) {
          var ext = require('path').extname(filepath),
              type = tree._mime._types[ext];
          if (type === undefined) {
              throw new Error('Optional dependency "mime" is required for ' + ext);
          }
          return type;
      },
      charsets: {
          lookup: function (type) {
              // assumes all text types are UTF-8
              return type && (/^text\//).test(type) ? 'UTF-8' : '';
          }
      }
  };
  
  // Math
  
  var mathFunctions = {
   // name,  unit
      ceil:  null, 
      floor: null, 
      sqrt:  null, 
      abs:   null,
      tan:   "", 
      sin:   "", 
      cos:   "",
      atan:  "rad", 
      asin:  "rad", 
      acos:  "rad"
  };
  
  function _math(fn, unit, n) {
      if (!(n instanceof tree.Dimension)) {
          throw { type: "Argument", message: "argument must be a number" };
      }
      if (unit == null) {
          unit = n.unit;
      } else {
          n = n.unify();
      }
      return new(tree.Dimension)(fn(parseFloat(n.value)), unit);
  }
  
  // ~ End of Math
  
  // Color Blending
  // ref: http://www.w3.org/TR/compositing-1
  
  function colorBlend(mode, color1, color2) {
      var ab = color1.alpha, cb, // backdrop
          as = color2.alpha, cs, // source
          ar, cr, r = [];        // result
          
      ar = as + ab * (1 - as);
      for (var i = 0; i < 3; i++) {
          cb = color1.rgb[i] / 255;
          cs = color2.rgb[i] / 255;
          cr = mode(cb, cs);
          if (ar) {
              cr = (as * cs + ab * (cb 
                  - as * (cb + cs - cr))) / ar;
          }
          r[i] = cr * 255;
      }
      
      return new(tree.Color)(r, ar);
  }
  
  var colorBlendMode = {
      multiply: function(cb, cs) {
          return cb * cs;
      },
      screen: function(cb, cs) {
          return cb + cs - cb * cs;
      },   
      overlay: function(cb, cs) {
          cb *= 2;
          return (cb <= 1)
              ? colorBlendMode.multiply(cb, cs)
              : colorBlendMode.screen(cb - 1, cs);
      },
      softlight: function(cb, cs) {
          var d = 1, e = cb;
          if (cs > 0.5) {
              e = 1;
              d = (cb > 0.25) ? Math.sqrt(cb)
                  : ((16 * cb - 12) * cb + 4) * cb;
          }            
          return cb - (1 - 2 * cs) * e * (d - cb);
      },
      hardlight: function(cb, cs) {
          return colorBlendMode.overlay(cs, cb);
      },
      difference: function(cb, cs) {
          return Math.abs(cb - cs);
      },
      exclusion: function(cb, cs) {
          return cb + cs - 2 * cb * cs;
      },
  
      // non-w3c functions:
      average: function(cb, cs) {
          return (cb + cs) / 2;
      },
      negation: function(cb, cs) {
          return 1 - Math.abs(cb + cs - 1);
      }
  };
  
  // ~ End of Color Blending
  
  tree.defaultFunc = {
      eval: function () {
          var v = this.value_, e = this.error_;
          if (e) {
              throw e;
          }
          if (v != null) {
              return v ? tree.True : tree.False;
          }
      },
      value: function (v) {
          this.value_ = v;
      },
      error: function (e) {
          this.error_ = e;
      },
      reset: function () {
          this.value_ = this.error_ = null;
      }
  };
  
  function initFunctions() {
      var f, tf = tree.functions;
      
      // math
      for (f in mathFunctions) {
          if (mathFunctions.hasOwnProperty(f)) {
              tf[f] = _math.bind(null, Math[f], mathFunctions[f]);
          }
      }
      
      // color blending
      for (f in colorBlendMode) {
          if (colorBlendMode.hasOwnProperty(f)) {
              tf[f] = colorBlend.bind(null, colorBlendMode[f]);
          }
      }
      
      // default
      f = tree.defaultFunc;
      tf["default"] = f.eval.bind(f);
      
  } initFunctions();
  
  function hsla(color) {
      return tree.functions.hsla(color.h, color.s, color.l, color.a);
  }
  
  function scaled(n, size) {
      if (n instanceof tree.Dimension && n.unit.is('%')) {
          return parseFloat(n.value * size / 100);
      } else {
          return number(n);
      }
  }
  
  function number(n) {
      if (n instanceof tree.Dimension) {
          return parseFloat(n.unit.is('%') ? n.value / 100 : n.value);
      } else if (typeof(n) === 'number') {
          return n;
      } else {
          throw {
              error: "RuntimeError",
              message: "color functions take numbers as parameters"
          };
      }
  }
  
  function clamp(val) {
      return Math.min(1, Math.max(0, val));
  }
  
  tree.fround = function(env, value) {
      var p;
      if (env && (env.numPrecision != null)) {
          p = Math.pow(10, env.numPrecision);
          return Math.round(value * p) / p;
      } else {
          return value;
      }
  };
  
  tree.functionCall = function(env, currentFileInfo) {
      this.env = env;
      this.currentFileInfo = currentFileInfo;
  };
  
  tree.functionCall.prototype = tree.functions;
  
  })(require('./tree'));
  
  (function (tree) {
      tree.colors = {
          'aliceblue':'#f0f8ff',
          'antiquewhite':'#faebd7',
          'aqua':'#00ffff',
          'aquamarine':'#7fffd4',
          'azure':'#f0ffff',
          'beige':'#f5f5dc',
          'bisque':'#ffe4c4',
          'black':'#000000',
          'blanchedalmond':'#ffebcd',
          'blue':'#0000ff',
          'blueviolet':'#8a2be2',
          'brown':'#a52a2a',
          'burlywood':'#deb887',
          'cadetblue':'#5f9ea0',
          'chartreuse':'#7fff00',
          'chocolate':'#d2691e',
          'coral':'#ff7f50',
          'cornflowerblue':'#6495ed',
          'cornsilk':'#fff8dc',
          'crimson':'#dc143c',
          'cyan':'#00ffff',
          'darkblue':'#00008b',
          'darkcyan':'#008b8b',
          'darkgoldenrod':'#b8860b',
          'darkgray':'#a9a9a9',
          'darkgrey':'#a9a9a9',
          'darkgreen':'#006400',
          'darkkhaki':'#bdb76b',
          'darkmagenta':'#8b008b',
          'darkolivegreen':'#556b2f',
          'darkorange':'#ff8c00',
          'darkorchid':'#9932cc',
          'darkred':'#8b0000',
          'darksalmon':'#e9967a',
          'darkseagreen':'#8fbc8f',
          'darkslateblue':'#483d8b',
          'darkslategray':'#2f4f4f',
          'darkslategrey':'#2f4f4f',
          'darkturquoise':'#00ced1',
          'darkviolet':'#9400d3',
          'deeppink':'#ff1493',
          'deepskyblue':'#00bfff',
          'dimgray':'#696969',
          'dimgrey':'#696969',
          'dodgerblue':'#1e90ff',
          'firebrick':'#b22222',
          'floralwhite':'#fffaf0',
          'forestgreen':'#228b22',
          'fuchsia':'#ff00ff',
          'gainsboro':'#dcdcdc',
          'ghostwhite':'#f8f8ff',
          'gold':'#ffd700',
          'goldenrod':'#daa520',
          'gray':'#808080',
          'grey':'#808080',
          'green':'#008000',
          'greenyellow':'#adff2f',
          'honeydew':'#f0fff0',
          'hotpink':'#ff69b4',
          'indianred':'#cd5c5c',
          'indigo':'#4b0082',
          'ivory':'#fffff0',
          'khaki':'#f0e68c',
          'lavender':'#e6e6fa',
          'lavenderblush':'#fff0f5',
          'lawngreen':'#7cfc00',
          'lemonchiffon':'#fffacd',
          'lightblue':'#add8e6',
          'lightcoral':'#f08080',
          'lightcyan':'#e0ffff',
          'lightgoldenrodyellow':'#fafad2',
          'lightgray':'#d3d3d3',
          'lightgrey':'#d3d3d3',
          'lightgreen':'#90ee90',
          'lightpink':'#ffb6c1',
          'lightsalmon':'#ffa07a',
          'lightseagreen':'#20b2aa',
          'lightskyblue':'#87cefa',
          'lightslategray':'#778899',
          'lightslategrey':'#778899',
          'lightsteelblue':'#b0c4de',
          'lightyellow':'#ffffe0',
          'lime':'#00ff00',
          'limegreen':'#32cd32',
          'linen':'#faf0e6',
          'magenta':'#ff00ff',
          'maroon':'#800000',
          'mediumaquamarine':'#66cdaa',
          'mediumblue':'#0000cd',
          'mediumorchid':'#ba55d3',
          'mediumpurple':'#9370d8',
          'mediumseagreen':'#3cb371',
          'mediumslateblue':'#7b68ee',
          'mediumspringgreen':'#00fa9a',
          'mediumturquoise':'#48d1cc',
          'mediumvioletred':'#c71585',
          'midnightblue':'#191970',
          'mintcream':'#f5fffa',
          'mistyrose':'#ffe4e1',
          'moccasin':'#ffe4b5',
          'navajowhite':'#ffdead',
          'navy':'#000080',
          'oldlace':'#fdf5e6',
          'olive':'#808000',
          'olivedrab':'#6b8e23',
          'orange':'#ffa500',
          'orangered':'#ff4500',
          'orchid':'#da70d6',
          'palegoldenrod':'#eee8aa',
          'palegreen':'#98fb98',
          'paleturquoise':'#afeeee',
          'palevioletred':'#d87093',
          'papayawhip':'#ffefd5',
          'peachpuff':'#ffdab9',
          'peru':'#cd853f',
          'pink':'#ffc0cb',
          'plum':'#dda0dd',
          'powderblue':'#b0e0e6',
          'purple':'#800080',
          'red':'#ff0000',
          'rosybrown':'#bc8f8f',
          'royalblue':'#4169e1',
          'saddlebrown':'#8b4513',
          'salmon':'#fa8072',
          'sandybrown':'#f4a460',
          'seagreen':'#2e8b57',
          'seashell':'#fff5ee',
          'sienna':'#a0522d',
          'silver':'#c0c0c0',
          'skyblue':'#87ceeb',
          'slateblue':'#6a5acd',
          'slategray':'#708090',
          'slategrey':'#708090',
          'snow':'#fffafa',
          'springgreen':'#00ff7f',
          'steelblue':'#4682b4',
          'tan':'#d2b48c',
          'teal':'#008080',
          'thistle':'#d8bfd8',
          'tomato':'#ff6347',
          'turquoise':'#40e0d0',
          'violet':'#ee82ee',
          'wheat':'#f5deb3',
          'white':'#ffffff',
          'whitesmoke':'#f5f5f5',
          'yellow':'#ffff00',
          'yellowgreen':'#9acd32'
      };
  })(require('./tree'));
  
  (function (tree) {
  
  tree.debugInfo = function(env, ctx, lineSeperator) {
      var result="";
      if (env.dumpLineNumbers && !env.compress) {
          switch(env.dumpLineNumbers) {
              case 'comments':
                  result = tree.debugInfo.asComment(ctx);
                  break;
              case 'mediaquery':
                  result = tree.debugInfo.asMediaQuery(ctx);
                  break;
              case 'all':
                  result = tree.debugInfo.asComment(ctx) + (lineSeperator || "") + tree.debugInfo.asMediaQuery(ctx);
                  break;
          }
      }
      return result;
  };
  
  tree.debugInfo.asComment = function(ctx) {
      return '/* line ' + ctx.debugInfo.lineNumber + ', ' + ctx.debugInfo.fileName + ' */\n';
  };
  
  tree.debugInfo.asMediaQuery = function(ctx) {
      return '@media -sass-debug-info{filename{font-family:' +
          ('file://' + ctx.debugInfo.fileName).replace(/([.:\/\\])/g, function (a) {
              if (a == '\\') {
                  a = '\/';
              }
              return '\\' + a;
          }) +
          '}line{font-family:\\00003' + ctx.debugInfo.lineNumber + '}}\n';
  };
  
  tree.find = function (obj, fun) {
      for (var i = 0, r; i < obj.length; i++) {
          r = fun.call(obj, obj[i]);
          if (r) { return r; }
      }
      return null;
  };
  
  tree.jsify = function (obj) {
      if (Array.isArray(obj.value) && (obj.value.length > 1)) {
          return '[' + obj.value.map(function (v) { return v.toCSS(false); }).join(', ') + ']';
      } else {
          return obj.toCSS(false);
      }
  };
  
  tree.toCSS = function (env) {
      var strs = [];
      this.genCSS(env, {
          add: function(chunk, fileInfo, index) {
              strs.push(chunk);
          },
          isEmpty: function () {
              return strs.length === 0;
          }
      });
      return strs.join('');
  };
  
  tree.outputRuleset = function (env, output, rules) {
      var ruleCnt = rules.length, i;
      env.tabLevel = (env.tabLevel | 0) + 1;
  
      // Compressed
      if (env.compress) {
          output.add('{');
          for (i = 0; i < ruleCnt; i++) {
              rules[i].genCSS(env, output);
          }
          output.add('}');
          env.tabLevel--;
          return;
      }
  
      // Non-compressed
      var tabSetStr = '\n' + Array(env.tabLevel).join("  "), tabRuleStr = tabSetStr + "  ";
      if (!ruleCnt) {
          output.add(" {" + tabSetStr + '}');
      } else {
          output.add(" {" + tabRuleStr);
          rules[0].genCSS(env, output);
          for (i = 1; i < ruleCnt; i++) {
              output.add(tabRuleStr);
              rules[i].genCSS(env, output);
          }
          output.add(tabSetStr + '}');
      }
  
      env.tabLevel--;
  };
  
  })(require('./tree'));
  
  (function (tree) {
  
  tree.Alpha = function (val) {
      this.value = val;
  };
  tree.Alpha.prototype = {
      type: "Alpha",
      accept: function (visitor) {
          this.value = visitor.visit(this.value);
      },
      eval: function (env) {
          if (this.value.eval) { return new tree.Alpha(this.value.eval(env)); }
          return this;
      },
      genCSS: function (env, output) {
          output.add("alpha(opacity=");
  
          if (this.value.genCSS) {
              this.value.genCSS(env, output);
          } else {
              output.add(this.value);
          }
  
          output.add(")");
      },
      toCSS: tree.toCSS
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Anonymous = function (string, index, currentFileInfo, mapLines) {
      this.value = string.value || string;
      this.index = index;
      this.mapLines = mapLines;
      this.currentFileInfo = currentFileInfo;
  };
  tree.Anonymous.prototype = {
      type: "Anonymous",
      eval: function () { 
          return new tree.Anonymous(this.value, this.index, this.currentFileInfo, this.mapLines);
      },
      compare: function (x) {
          if (!x.toCSS) {
              return -1;
          }
          
          var left = this.toCSS(),
              right = x.toCSS();
          
          if (left === right) {
              return 0;
          }
          
          return left < right ? -1 : 1;
      },
      genCSS: function (env, output) {
          output.add(this.value, this.currentFileInfo, this.index, this.mapLines);
      },
      toCSS: tree.toCSS
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Assignment = function (key, val) {
      this.key = key;
      this.value = val;
  };
  tree.Assignment.prototype = {
      type: "Assignment",
      accept: function (visitor) {
          this.value = visitor.visit(this.value);
      },
      eval: function (env) {
          if (this.value.eval) {
              return new(tree.Assignment)(this.key, this.value.eval(env));
          }
          return this;
      },
      genCSS: function (env, output) {
          output.add(this.key + '=');
          if (this.value.genCSS) {
              this.value.genCSS(env, output);
          } else {
              output.add(this.value);
          }
      },
      toCSS: tree.toCSS
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  //
  // A function call node.
  //
  tree.Call = function (name, args, index, currentFileInfo) {
      this.name = name;
      this.args = args;
      this.index = index;
      this.currentFileInfo = currentFileInfo;
  };
  tree.Call.prototype = {
      type: "Call",
      accept: function (visitor) {
          if (this.args) {
              this.args = visitor.visitArray(this.args);
          }
      },
      //
      // When evaluating a function call,
      // we either find the function in `tree.functions` [1],
      // in which case we call it, passing the  evaluated arguments,
      // if this returns null or we cannot find the function, we 
      // simply print it out as it appeared originally [2].
      //
      // The *functions.js* file contains the built-in functions.
      //
      // The reason why we evaluate the arguments, is in the case where
      // we try to pass a variable to a function, like: `saturate(@color)`.
      // The function should receive the value, not the variable.
      //
      eval: function (env) {
          var args = this.args.map(function (a) { return a.eval(env); }),
              nameLC = this.name.toLowerCase(),
              result, func;
  
          if (nameLC in tree.functions) { // 1.
              try {
                  func = new tree.functionCall(env, this.currentFileInfo);
                  result = func[nameLC].apply(func, args);
                  if (result != null) {
                      return result;
                  }
              } catch (e) {
                  throw { type: e.type || "Runtime",
                          message: "error evaluating function `" + this.name + "`" +
                                   (e.message ? ': ' + e.message : ''),
                          index: this.index, filename: this.currentFileInfo.filename };
              }
          }
  
          return new tree.Call(this.name, args, this.index, this.currentFileInfo);
      },
  
      genCSS: function (env, output) {
          output.add(this.name + "(", this.currentFileInfo, this.index);
  
          for(var i = 0; i < this.args.length; i++) {
              this.args[i].genCSS(env, output);
              if (i + 1 < this.args.length) {
                  output.add(", ");
              }
          }
  
          output.add(")");
      },
  
      toCSS: tree.toCSS
  };
  
  })(require('../tree'));
  
  (function (tree) {
  //
  // RGB Colors - #ff0014, #eee
  //
  tree.Color = function (rgb, a) {
      //
      // The end goal here, is to parse the arguments
      // into an integer triplet, such as `128, 255, 0`
      //
      // This facilitates operations and conversions.
      //
      if (Array.isArray(rgb)) {
          this.rgb = rgb;
      } else if (rgb.length == 6) {
          this.rgb = rgb.match(/.{2}/g).map(function (c) {
              return parseInt(c, 16);
          });
      } else {
          this.rgb = rgb.split('').map(function (c) {
              return parseInt(c + c, 16);
          });
      }
      this.alpha = typeof(a) === 'number' ? a : 1;
  };
  
  var transparentKeyword = "transparent";
  
  tree.Color.prototype = {
      type: "Color",
      eval: function () { return this; },
      luma: function () { return (0.2126 * this.rgb[0] / 255) + (0.7152 * this.rgb[1] / 255) + (0.0722 * this.rgb[2] / 255); },
  
      genCSS: function (env, output) {
          output.add(this.toCSS(env));
      },
      toCSS: function (env, doNotCompress) {
          var compress = env && env.compress && !doNotCompress,
              alpha = tree.fround(env, this.alpha);
  
          // If we have some transparency, the only way to represent it
          // is via `rgba`. Otherwise, we use the hex representation,
          // which has better compatibility with older browsers.
          // Values are capped between `0` and `255`, rounded and zero-padded.
          if (alpha < 1) {
              if (alpha === 0 && this.isTransparentKeyword) {
                  return transparentKeyword;
              }
              return "rgba(" + this.rgb.map(function (c) {
                  return clamp(Math.round(c), 255);
              }).concat(clamp(alpha, 1))
                  .join(',' + (compress ? '' : ' ')) + ")";
          } else {
              var color = this.toRGB();
  
              if (compress) {
                  var splitcolor = color.split('');
  
                  // Convert color to short format
                  if (splitcolor[1] === splitcolor[2] && splitcolor[3] === splitcolor[4] && splitcolor[5] === splitcolor[6]) {
                      color = '#' + splitcolor[1] + splitcolor[3] + splitcolor[5];
                  }
              }
  
              return color;
          }
      },
  
      //
      // Operations have to be done per-channel, if not,
      // channels will spill onto each other. Once we have
      // our result, in the form of an integer triplet,
      // we create a new Color node to hold the result.
      //
      operate: function (env, op, other) {
          var rgb = [];
          var alpha = this.alpha * (1 - other.alpha) + other.alpha;
          for (var c = 0; c < 3; c++) {
              rgb[c] = tree.operate(env, op, this.rgb[c], other.rgb[c]);
          }
          return new(tree.Color)(rgb, alpha);
      },
  
      toRGB: function () {
          return toHex(this.rgb);
      },
  
      toHSL: function () {
          var r = this.rgb[0] / 255,
              g = this.rgb[1] / 255,
              b = this.rgb[2] / 255,
              a = this.alpha;
  
          var max = Math.max(r, g, b), min = Math.min(r, g, b);
          var h, s, l = (max + min) / 2, d = max - min;
  
          if (max === min) {
              h = s = 0;
          } else {
              s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
  
              switch (max) {
                  case r: h = (g - b) / d + (g < b ? 6 : 0); break;
                  case g: h = (b - r) / d + 2;               break;
                  case b: h = (r - g) / d + 4;               break;
              }
              h /= 6;
          }
          return { h: h * 360, s: s, l: l, a: a };
      },
      //Adapted from http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
      toHSV: function () {
          var r = this.rgb[0] / 255,
              g = this.rgb[1] / 255,
              b = this.rgb[2] / 255,
              a = this.alpha;
  
          var max = Math.max(r, g, b), min = Math.min(r, g, b);
          var h, s, v = max;
  
          var d = max - min;
          if (max === 0) {
              s = 0;
          } else {
              s = d / max;
          }
  
          if (max === min) {
              h = 0;
          } else {
              switch(max){
                  case r: h = (g - b) / d + (g < b ? 6 : 0); break;
                  case g: h = (b - r) / d + 2; break;
                  case b: h = (r - g) / d + 4; break;
              }
              h /= 6;
          }
          return { h: h * 360, s: s, v: v, a: a };
      },
      toARGB: function () {
          return toHex([this.alpha * 255].concat(this.rgb));
      },
      compare: function (x) {
          if (!x.rgb) {
              return -1;
          }
          
          return (x.rgb[0] === this.rgb[0] &&
              x.rgb[1] === this.rgb[1] &&
              x.rgb[2] === this.rgb[2] &&
              x.alpha === this.alpha) ? 0 : -1;
      }
  };
  
  tree.Color.fromKeyword = function(keyword) {
      keyword = keyword.toLowerCase();
  
      if (tree.colors.hasOwnProperty(keyword)) {
          // detect named color
          return new(tree.Color)(tree.colors[keyword].slice(1));
      }
      if (keyword === transparentKeyword) {
          var transparent = new(tree.Color)([0, 0, 0], 0);
          transparent.isTransparentKeyword = true;
          return transparent;
      }
  };
  
  function toHex(v) {
      return '#' + v.map(function (c) {
          c = clamp(Math.round(c), 255);
          return (c < 16 ? '0' : '') + c.toString(16);
      }).join('');
  }
  
  function clamp(v, max) {
      return Math.min(Math.max(v, 0), max); 
  }
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Comment = function (value, silent, index, currentFileInfo) {
      this.value = value;
      this.silent = !!silent;
      this.currentFileInfo = currentFileInfo;
  };
  tree.Comment.prototype = {
      type: "Comment",
      genCSS: function (env, output) {
          if (this.debugInfo) {
              output.add(tree.debugInfo(env, this), this.currentFileInfo, this.index);
          }
          output.add(this.value.trim()); //TODO shouldn't need to trim, we shouldn't grab the \n
      },
      toCSS: tree.toCSS,
      isSilent: function(env) {
          var isReference = (this.currentFileInfo && this.currentFileInfo.reference && !this.isReferenced),
              isCompressed = env.compress && !this.value.match(/^\/\*!/);
          return this.silent || isReference || isCompressed;
      },
      eval: function () { return this; },
      markReferenced: function () {
          this.isReferenced = true;
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Condition = function (op, l, r, i, negate) {
      this.op = op.trim();
      this.lvalue = l;
      this.rvalue = r;
      this.index = i;
      this.negate = negate;
  };
  tree.Condition.prototype = {
      type: "Condition",
      accept: function (visitor) {
          this.lvalue = visitor.visit(this.lvalue);
          this.rvalue = visitor.visit(this.rvalue);
      },
      eval: function (env) {
          var a = this.lvalue.eval(env),
              b = this.rvalue.eval(env);
  
          var i = this.index, result;
  
          result = (function (op) {
              switch (op) {
                  case 'and':
                      return a && b;
                  case 'or':
                      return a || b;
                  default:
                      if (a.compare) {
                          result = a.compare(b);
                      } else if (b.compare) {
                          result = b.compare(a);
                      } else {
                          throw { type: "Type",
                                  message: "Unable to perform comparison",
                                  index: i };
                      }
                      switch (result) {
                          case -1: return op === '<' || op === '=<' || op === '<=';
                          case  0: return op === '=' || op === '>=' || op === '=<' || op === '<=';
                          case  1: return op === '>' || op === '>=';
                      }
              }
          })(this.op);
          return this.negate ? !result : result;
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  //
  // A number with a unit
  //
  tree.Dimension = function (value, unit) {
      this.value = parseFloat(value);
      this.unit = (unit && unit instanceof tree.Unit) ? unit :
        new(tree.Unit)(unit ? [unit] : undefined);
  };
  
  tree.Dimension.prototype = {
      type: "Dimension",
      accept: function (visitor) {
          this.unit = visitor.visit(this.unit);
      },
      eval: function (env) {
          return this;
      },
      toColor: function () {
          return new(tree.Color)([this.value, this.value, this.value]);
      },
      genCSS: function (env, output) {
          if ((env && env.strictUnits) && !this.unit.isSingular()) {
              throw new Error("Multiple units in dimension. Correct the units or use the unit function. Bad unit: "+this.unit.toString());
          }
  
          var value = tree.fround(env, this.value),
              strValue = String(value);
  
          if (value !== 0 && value < 0.000001 && value > -0.000001) {
              // would be output 1e-6 etc.
              strValue = value.toFixed(20).replace(/0+$/, "");
          }
  
          if (env && env.compress) {
              // Zero values doesn't need a unit
              if (value === 0 && this.unit.isLength()) {
                  output.add(strValue);
                  return;
              }
  
              // Float values doesn't need a leading zero
              if (value > 0 && value < 1) {
                  strValue = (strValue).substr(1);
              }
          }
  
          output.add(strValue);
          this.unit.genCSS(env, output);
      },
      toCSS: tree.toCSS,
  
      // In an operation between two Dimensions,
      // we default to the first Dimension's unit,
      // so `1px + 2` will yield `3px`.
      operate: function (env, op, other) {
          /*jshint noempty:false */
          var value = tree.operate(env, op, this.value, other.value),
              unit = this.unit.clone();
  
          if (op === '+' || op === '-') {
              if (unit.numerator.length === 0 && unit.denominator.length === 0) {
                  unit.numerator = other.unit.numerator.slice(0);
                  unit.denominator = other.unit.denominator.slice(0);
              } else if (other.unit.numerator.length === 0 && unit.denominator.length === 0) {
                  // do nothing
              } else {
                  other = other.convertTo(this.unit.usedUnits());
  
                  if(env.strictUnits && other.unit.toString() !== unit.toString()) {
                    throw new Error("Incompatible units. Change the units or use the unit function. Bad units: '" + unit.toString() +
                      "' and '" + other.unit.toString() + "'.");
                  }
  
                  value = tree.operate(env, op, this.value, other.value);
              }
          } else if (op === '*') {
              unit.numerator = unit.numerator.concat(other.unit.numerator).sort();
              unit.denominator = unit.denominator.concat(other.unit.denominator).sort();
              unit.cancel();
          } else if (op === '/') {
              unit.numerator = unit.numerator.concat(other.unit.denominator).sort();
              unit.denominator = unit.denominator.concat(other.unit.numerator).sort();
              unit.cancel();
          }
          return new(tree.Dimension)(value, unit);
      },
  
      compare: function (other) {
          if (other instanceof tree.Dimension) {
              var a = this.unify(), b = other.unify(),
                  aValue = a.value, bValue = b.value;
  
              if (bValue > aValue) {
                  return -1;
              } else if (bValue < aValue) {
                  return 1;
              } else {
                  if (!b.unit.isEmpty() && a.unit.compare(b.unit) !== 0) {
                      return -1;
                  }
                  return 0;
              }
          } else {
              return -1;
          }
      },
  
      unify: function () {
          return this.convertTo({ length: 'm', duration: 's', angle: 'rad' });
      },
  
      convertTo: function (conversions) {
          var value = this.value, unit = this.unit.clone(),
              i, groupName, group, targetUnit, derivedConversions = {}, applyUnit;
  
          if (typeof conversions === 'string') {
              for(i in tree.UnitConversions) {
                  if (tree.UnitConversions[i].hasOwnProperty(conversions)) {
                      derivedConversions = {};
                      derivedConversions[i] = conversions;
                  }
              }
              conversions = derivedConversions;
          }
          applyUnit = function (atomicUnit, denominator) {
            /*jshint loopfunc:true */
              if (group.hasOwnProperty(atomicUnit)) {
                  if (denominator) {
                      value = value / (group[atomicUnit] / group[targetUnit]);
                  } else {
                      value = value * (group[atomicUnit] / group[targetUnit]);
                  }
  
                  return targetUnit;
              }
  
              return atomicUnit;
          };
  
          for (groupName in conversions) {
              if (conversions.hasOwnProperty(groupName)) {
                  targetUnit = conversions[groupName];
                  group = tree.UnitConversions[groupName];
  
                  unit.map(applyUnit);
              }
          }
  
          unit.cancel();
  
          return new(tree.Dimension)(value, unit);
      }
  };
  
  // http://www.w3.org/TR/css3-values/#absolute-lengths
  tree.UnitConversions = {
      length: {
           'm': 1,
          'cm': 0.01,
          'mm': 0.001,
          'in': 0.0254,
          'pt': 0.0254 / 72,
          'pc': 0.0254 / 72 * 12
      },
      duration: {
          's': 1,
          'ms': 0.001
      },
      angle: {
          'rad': 1/(2*Math.PI),
          'deg': 1/360,
          'grad': 1/400,
          'turn': 1
      }
  };
  
  tree.Unit = function (numerator, denominator, backupUnit) {
      this.numerator = numerator ? numerator.slice(0).sort() : [];
      this.denominator = denominator ? denominator.slice(0).sort() : [];
      this.backupUnit = backupUnit;
  };
  
  tree.Unit.prototype = {
      type: "Unit",
      clone: function () {
          return new tree.Unit(this.numerator.slice(0), this.denominator.slice(0), this.backupUnit);
      },
      genCSS: function (env, output) {
          if (this.numerator.length >= 1) {
              output.add(this.numerator[0]);
          } else
          if (this.denominator.length >= 1) {
              output.add(this.denominator[0]);
          } else
          if ((!env || !env.strictUnits) && this.backupUnit) {
              output.add(this.backupUnit);
          }
      },
      toCSS: tree.toCSS,
  
      toString: function () {
        var i, returnStr = this.numerator.join("*");
        for (i = 0; i < this.denominator.length; i++) {
            returnStr += "/" + this.denominator[i];
        }
        return returnStr;
      },
  
      compare: function (other) {
          return this.is(other.toString()) ? 0 : -1;
      },
  
      is: function (unitString) {
          return this.toString() === unitString;
      },
  
      isLength: function () {
          return Boolean(this.toCSS().match(/px|em|%|in|cm|mm|pc|pt|ex/));
      },
  
      isEmpty: function () {
          return this.numerator.length === 0 && this.denominator.length === 0;
      },
  
      isSingular: function() {
          return this.numerator.length <= 1 && this.denominator.length === 0;
      },
  
      map: function(callback) {
          var i;
  
          for (i = 0; i < this.numerator.length; i++) {
              this.numerator[i] = callback(this.numerator[i], false);
          }
  
          for (i = 0; i < this.denominator.length; i++) {
              this.denominator[i] = callback(this.denominator[i], true);
          }
      },
  
      usedUnits: function() {
          var group, result = {}, mapUnit;
  
          mapUnit = function (atomicUnit) {
          /*jshint loopfunc:true */
              if (group.hasOwnProperty(atomicUnit) && !result[groupName]) {
                  result[groupName] = atomicUnit;
              }
  
              return atomicUnit;
          };
  
          for (var groupName in tree.UnitConversions) {
              if (tree.UnitConversions.hasOwnProperty(groupName)) {
                  group = tree.UnitConversions[groupName];
  
                  this.map(mapUnit);
              }
          }
  
          return result;
      },
  
      cancel: function () {
          var counter = {}, atomicUnit, i, backup;
  
          for (i = 0; i < this.numerator.length; i++) {
              atomicUnit = this.numerator[i];
              if (!backup) {
                  backup = atomicUnit;
              }
              counter[atomicUnit] = (counter[atomicUnit] || 0) + 1;
          }
  
          for (i = 0; i < this.denominator.length; i++) {
              atomicUnit = this.denominator[i];
              if (!backup) {
                  backup = atomicUnit;
              }
              counter[atomicUnit] = (counter[atomicUnit] || 0) - 1;
          }
  
          this.numerator = [];
          this.denominator = [];
  
          for (atomicUnit in counter) {
              if (counter.hasOwnProperty(atomicUnit)) {
                  var count = counter[atomicUnit];
  
                  if (count > 0) {
                      for (i = 0; i < count; i++) {
                          this.numerator.push(atomicUnit);
                      }
                  } else if (count < 0) {
                      for (i = 0; i < -count; i++) {
                          this.denominator.push(atomicUnit);
                      }
                  }
              }
          }
  
          if (this.numerator.length === 0 && this.denominator.length === 0 && backup) {
              this.backupUnit = backup;
          }
  
          this.numerator.sort();
          this.denominator.sort();
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Directive = function (name, value, index, currentFileInfo) {
      this.name = name;
  
      if (Array.isArray(value)) {
          this.rules = [new(tree.Ruleset)(null, value)];
          this.rules[0].allowImports = true;
      } else {
          this.value = value;
      }
      this.index = index;
      this.currentFileInfo = currentFileInfo;
  
  };
  tree.Directive.prototype = {
      type: "Directive",
      accept: function (visitor) {
          if (this.rules) {
              this.rules = visitor.visitArray(this.rules);
          }
          if (this.value) {
              this.value = visitor.visit(this.value);
          }
      },
      genCSS: function (env, output) {
          output.add(this.name, this.currentFileInfo, this.index);
          if (this.rules) {
              tree.outputRuleset(env, output, this.rules);
          } else {
              output.add(' ');
              this.value.genCSS(env, output);
              output.add(';');
          }
      },
      toCSS: tree.toCSS,
      eval: function (env) {
          var evaldDirective = this;
          if (this.rules) {
              env.frames.unshift(this);
              evaldDirective = new(tree.Directive)(this.name, null, this.index, this.currentFileInfo);
              evaldDirective.rules = [this.rules[0].eval(env)];
              evaldDirective.rules[0].root = true;
              env.frames.shift();
          }
          return evaldDirective;
      },
      variable: function (name) { return tree.Ruleset.prototype.variable.call(this.rules[0], name); },
      find: function () { return tree.Ruleset.prototype.find.apply(this.rules[0], arguments); },
      rulesets: function () { return tree.Ruleset.prototype.rulesets.apply(this.rules[0]); },
      markReferenced: function () {
          var i, rules;
          this.isReferenced = true;
          if (this.rules) {
              rules = this.rules[0].rules;
              for (i = 0; i < rules.length; i++) {
                  if (rules[i].markReferenced) {
                      rules[i].markReferenced();
                  }
              }
          }
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Element = function (combinator, value, index, currentFileInfo) {
      this.combinator = combinator instanceof tree.Combinator ?
                        combinator : new(tree.Combinator)(combinator);
  
      if (typeof(value) === 'string') {
          this.value = value.trim();
      } else if (value) {
          this.value = value;
      } else {
          this.value = "";
      }
      this.index = index;
      this.currentFileInfo = currentFileInfo;
  };
  tree.Element.prototype = {
      type: "Element",
      accept: function (visitor) {
          var value = this.value;
          this.combinator = visitor.visit(this.combinator);
          if (typeof value === "object") {
              this.value = visitor.visit(value);
          }
      },
      eval: function (env) {
          return new(tree.Element)(this.combinator,
                                   this.value.eval ? this.value.eval(env) : this.value,
                                   this.index,
                                   this.currentFileInfo);
      },
      genCSS: function (env, output) {
          output.add(this.toCSS(env), this.currentFileInfo, this.index);
      },
      toCSS: function (env) {
          var value = (this.value.toCSS ? this.value.toCSS(env) : this.value);
          if (value === '' && this.combinator.value.charAt(0) === '&') {
              return '';
          } else {
              return this.combinator.toCSS(env || {}) + value;
          }
      }
  };
  
  tree.Attribute = function (key, op, value) {
      this.key = key;
      this.op = op;
      this.value = value;
  };
  tree.Attribute.prototype = {
      type: "Attribute",
      eval: function (env) {
          return new(tree.Attribute)(this.key.eval ? this.key.eval(env) : this.key,
              this.op, (this.value && this.value.eval) ? this.value.eval(env) : this.value);
      },
      genCSS: function (env, output) {
          output.add(this.toCSS(env));
      },
      toCSS: function (env) {
          var value = this.key.toCSS ? this.key.toCSS(env) : this.key;
  
          if (this.op) {
              value += this.op;
              value += (this.value.toCSS ? this.value.toCSS(env) : this.value);
          }
  
          return '[' + value + ']';
      }
  };
  
  tree.Combinator = function (value) {
      if (value === ' ') {
          this.value = ' ';
      } else {
          this.value = value ? value.trim() : "";
      }
  };
  tree.Combinator.prototype = {
      type: "Combinator",
      _outputMap: {
          ''  : '',
          ' ' : ' ',
          ':' : ' :',
          '+' : ' + ',
          '~' : ' ~ ',
          '>' : ' > ',
          '|' : '|',
          '^' : ' ^ ',
          '^^' : ' ^^ '
      },
      _outputMapCompressed: {
          ''  : '',
          ' ' : ' ',
          ':' : ' :',
          '+' : '+',
          '~' : '~',
          '>' : '>',
          '|' : '|',
          '^' : '^',
          '^^' : '^^'
      },
      genCSS: function (env, output) {
          output.add((env.compress ? this._outputMapCompressed : this._outputMap)[this.value]);
      },
      toCSS: tree.toCSS
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Expression = function (value) { this.value = value; };
  tree.Expression.prototype = {
      type: "Expression",
      accept: function (visitor) {
          if (this.value) {
              this.value = visitor.visitArray(this.value);
          }
      },
      eval: function (env) {
          var returnValue,
              inParenthesis = this.parens && !this.parensInOp,
              doubleParen = false;
          if (inParenthesis) {
              env.inParenthesis();
          }
          if (this.value.length > 1) {
              returnValue = new(tree.Expression)(this.value.map(function (e) {
                  return e.eval(env);
              }));
          } else if (this.value.length === 1) {
              if (this.value[0].parens && !this.value[0].parensInOp) {
                  doubleParen = true;
              }
              returnValue = this.value[0].eval(env);
          } else {
              returnValue = this;
          }
          if (inParenthesis) {
              env.outOfParenthesis();
          }
          if (this.parens && this.parensInOp && !(env.isMathOn()) && !doubleParen) {
              returnValue = new(tree.Paren)(returnValue);
          }
          return returnValue;
      },
      genCSS: function (env, output) {
          for(var i = 0; i < this.value.length; i++) {
              this.value[i].genCSS(env, output);
              if (i + 1 < this.value.length) {
                  output.add(" ");
              }
          }
      },
      toCSS: tree.toCSS,
      throwAwayComments: function () {
          this.value = this.value.filter(function(v) {
              return !(v instanceof tree.Comment);
          });
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Extend = function Extend(selector, option, index) {
      this.selector = selector;
      this.option = option;
      this.index = index;
      this.object_id = tree.Extend.next_id++;
      this.parent_ids = [this.object_id];
  
      switch(option) {
          case "all":
              this.allowBefore = true;
              this.allowAfter = true;
          break;
          default:
              this.allowBefore = false;
              this.allowAfter = false;
          break;
      }
  };
  tree.Extend.next_id = 0;
  
  tree.Extend.prototype = {
      type: "Extend",
      accept: function (visitor) {
          this.selector = visitor.visit(this.selector);
      },
      eval: function (env) {
          return new(tree.Extend)(this.selector.eval(env), this.option, this.index);
      },
      clone: function (env) {
          return new(tree.Extend)(this.selector, this.option, this.index);
      },
      findSelfSelectors: function (selectors) {
          var selfElements = [],
              i,
              selectorElements;
  
          for(i = 0; i < selectors.length; i++) {
              selectorElements = selectors[i].elements;
              // duplicate the logic in genCSS function inside the selector node.
              // future TODO - move both logics into the selector joiner visitor
              if (i > 0 && selectorElements.length && selectorElements[0].combinator.value === "") {
                  selectorElements[0].combinator.value = ' ';
              }
              selfElements = selfElements.concat(selectors[i].elements);
          }
  
          this.selfSelectors = [{ elements: selfElements }];
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  //
  // CSS @import node
  //
  // The general strategy here is that we don't want to wait
  // for the parsing to be completed, before we start importing
  // the file. That's because in the context of a browser,
  // most of the time will be spent waiting for the server to respond.
  //
  // On creation, we push the import path to our import queue, though
  // `import,push`, we also pass it a callback, which it'll call once
  // the file has been fetched, and parsed.
  //
  tree.Import = function (path, features, options, index, currentFileInfo) {
      this.options = options;
      this.index = index;
      this.path = path;
      this.features = features;
      this.currentFileInfo = currentFileInfo;
  
      if (this.options.less !== undefined || this.options.inline) {
          this.css = !this.options.less || this.options.inline;
      } else {
          var pathValue = this.getPath();
          if (pathValue && /css([\?;].*)?$/.test(pathValue)) {
              this.css = true;
          }
      }
  };
  
  //
  // The actual import node doesn't return anything, when converted to CSS.
  // The reason is that it's used at the evaluation stage, so that the rules
  // it imports can be treated like any other rules.
  //
  // In `eval`, we make sure all Import nodes get evaluated, recursively, so
  // we end up with a flat structure, which can easily be imported in the parent
  // ruleset.
  //
  tree.Import.prototype = {
      type: "Import",
      accept: function (visitor) {
          if (this.features) {
              this.features = visitor.visit(this.features);
          }
          this.path = visitor.visit(this.path);
          if (!this.options.inline && this.root) {
              this.root = visitor.visit(this.root);
          }
      },
      genCSS: function (env, output) {
          if (this.css) {
              output.add("@import ", this.currentFileInfo, this.index);
              this.path.genCSS(env, output);
              if (this.features) {
                  output.add(" ");
                  this.features.genCSS(env, output);
              }
              output.add(';');
          }
      },
      toCSS: tree.toCSS,
      getPath: function () {
          if (this.path instanceof tree.Quoted) {
              var path = this.path.value;
              return (this.css !== undefined || /(\.[a-z]*$)|([\?;].*)$/.test(path)) ? path : path + '.less';
          } else if (this.path instanceof tree.URL) {
              return this.path.value.value;
          }
          return null;
      },
      evalForImport: function (env) {
          return new(tree.Import)(this.path.eval(env), this.features, this.options, this.index, this.currentFileInfo);
      },
      evalPath: function (env) {
          var path = this.path.eval(env);
          var rootpath = this.currentFileInfo && this.currentFileInfo.rootpath;
  
          if (!(path instanceof tree.URL)) {
              if (rootpath) {
                  var pathValue = path.value;
                  // Add the base path if the import is relative
                  if (pathValue && env.isPathRelative(pathValue)) {
                      path.value = rootpath +pathValue;
                  }
              }
              path.value = env.normalizePath(path.value);
          }
  
          return path;
      },
      eval: function (env) {
          var ruleset, features = this.features && this.features.eval(env);
  
          if (this.skip) { return []; }
           
          if (this.options.inline) {
              //todo needs to reference css file not import
              var contents = new(tree.Anonymous)(this.root, 0, {filename: this.importedFilename}, true);
              return this.features ? new(tree.Media)([contents], this.features.value) : [contents];
          } else if (this.css) {
              var newImport = new(tree.Import)(this.evalPath(env), features, this.options, this.index);
              if (!newImport.css && this.error) {
                  throw this.error;
              }
              return newImport;
          } else {
              ruleset = new(tree.Ruleset)(null, this.root.rules.slice(0));
  
              ruleset.evalImports(env);
  
              return this.features ? new(tree.Media)(ruleset.rules, this.features.value) : ruleset.rules;
          }
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.JavaScript = function (string, index, escaped) {
      this.escaped = escaped;
      this.expression = string;
      this.index = index;
  };
  tree.JavaScript.prototype = {
      type: "JavaScript",
      eval: function (env) {
          var result,
              that = this,
              context = {};
  
          var expression = this.expression.replace(/@\{([\w-]+)\}/g, function (_, name) {
              return tree.jsify(new(tree.Variable)('@' + name, that.index).eval(env));
          });
  
          try {
              expression = new(Function)('return (' + expression + ')');
          } catch (e) {
              throw { message: "JavaScript evaluation error: " + e.message + " from `" + expression + "`" ,
                      index: this.index };
          }
  
          var variables = env.frames[0].variables();
          for (var k in variables) {
              if (variables.hasOwnProperty(k)) {
                  /*jshint loopfunc:true */
                  context[k.slice(1)] = {
                      value: variables[k].value,
                      toJS: function () {
                          return this.value.eval(env).toCSS();
                      }
                  };
              }
          }
  
          try {
              result = expression.call(context);
          } catch (e) {
              throw { message: "JavaScript evaluation error: '" + e.name + ': ' + e.message.replace(/["]/g, "'") + "'" ,
                      index: this.index };
          }
          if (typeof(result) === 'number') {
              return new(tree.Dimension)(result);
          } else if (typeof(result) === 'string') {
              return new(tree.Quoted)('"' + result + '"', result, this.escaped, this.index);
          } else if (Array.isArray(result)) {
              return new(tree.Anonymous)(result.join(', '));
          } else {
              return new(tree.Anonymous)(result);
          }
      }
  };
  
  })(require('../tree'));
  
  
  (function (tree) {
  
  tree.Keyword = function (value) { this.value = value; };
  tree.Keyword.prototype = {
      type: "Keyword",
      eval: function () { return this; },
      genCSS: function (env, output) {
          output.add(this.value);
      },
      toCSS: tree.toCSS,
      compare: function (other) {
          if (other instanceof tree.Keyword) {
              return other.value === this.value ? 0 : 1;
          } else {
              return -1;
          }
      }
  };
  
  tree.True = new(tree.Keyword)('true');
  tree.False = new(tree.Keyword)('false');
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Media = function (value, features, index, currentFileInfo) {
      this.index = index;
      this.currentFileInfo = currentFileInfo;
  
      var selectors = this.emptySelectors();
  
      this.features = new(tree.Value)(features);
      this.rules = [new(tree.Ruleset)(selectors, value)];
      this.rules[0].allowImports = true;
  };
  tree.Media.prototype = {
      type: "Media",
      accept: function (visitor) {
          if (this.features) {
              this.features = visitor.visit(this.features);
          }
          if (this.rules) {
              this.rules = visitor.visitArray(this.rules);
          }
      },
      genCSS: function (env, output) {
          output.add('@media ', this.currentFileInfo, this.index);
          this.features.genCSS(env, output);
          tree.outputRuleset(env, output, this.rules);
      },
      toCSS: tree.toCSS,
      eval: function (env) {
          if (!env.mediaBlocks) {
              env.mediaBlocks = [];
              env.mediaPath = [];
          }
          
          var media = new(tree.Media)(null, [], this.index, this.currentFileInfo);
          if(this.debugInfo) {
              this.rules[0].debugInfo = this.debugInfo;
              media.debugInfo = this.debugInfo;
          }
          var strictMathBypass = false;
          if (!env.strictMath) {
              strictMathBypass = true;
              env.strictMath = true;
          }
          try {
              media.features = this.features.eval(env);
          }
          finally {
              if (strictMathBypass) {
                  env.strictMath = false;
              }
          }
          
          env.mediaPath.push(media);
          env.mediaBlocks.push(media);
          
          env.frames.unshift(this.rules[0]);
          media.rules = [this.rules[0].eval(env)];
          env.frames.shift();
          
          env.mediaPath.pop();
  
          return env.mediaPath.length === 0 ? media.evalTop(env) :
                      media.evalNested(env);
      },
      variable: function (name) { return tree.Ruleset.prototype.variable.call(this.rules[0], name); },
      find: function () { return tree.Ruleset.prototype.find.apply(this.rules[0], arguments); },
      rulesets: function () { return tree.Ruleset.prototype.rulesets.apply(this.rules[0]); },
      emptySelectors: function() { 
          var el = new(tree.Element)('', '&', this.index, this.currentFileInfo),
              sels = [new(tree.Selector)([el], null, null, this.index, this.currentFileInfo)];
          sels[0].mediaEmpty = true;
          return sels;
      },
      markReferenced: function () {
          var i, rules = this.rules[0].rules;
          this.isReferenced = true;
          for (i = 0; i < rules.length; i++) {
              if (rules[i].markReferenced) {
                  rules[i].markReferenced();
              }
          }
      },
  
      evalTop: function (env) {
          var result = this;
  
          // Render all dependent Media blocks.
          if (env.mediaBlocks.length > 1) {
              var selectors = this.emptySelectors();
              result = new(tree.Ruleset)(selectors, env.mediaBlocks);
              result.multiMedia = true;
          }
  
          delete env.mediaBlocks;
          delete env.mediaPath;
  
          return result;
      },
      evalNested: function (env) {
          var i, value,
              path = env.mediaPath.concat([this]);
  
          // Extract the media-query conditions separated with `,` (OR).
          for (i = 0; i < path.length; i++) {
              value = path[i].features instanceof tree.Value ?
                          path[i].features.value : path[i].features;
              path[i] = Array.isArray(value) ? value : [value];
          }
  
          // Trace all permutations to generate the resulting media-query.
          //
          // (a, b and c) with nested (d, e) ->
          //    a and d
          //    a and e
          //    b and c and d
          //    b and c and e
          this.features = new(tree.Value)(this.permute(path).map(function (path) {
              path = path.map(function (fragment) {
                  return fragment.toCSS ? fragment : new(tree.Anonymous)(fragment);
              });
  
              for(i = path.length - 1; i > 0; i--) {
                  path.splice(i, 0, new(tree.Anonymous)("and"));
              }
  
              return new(tree.Expression)(path);
          }));
  
          // Fake a tree-node that doesn't output anything.
          return new(tree.Ruleset)([], []);
      },
      permute: function (arr) {
        if (arr.length === 0) {
            return [];
        } else if (arr.length === 1) {
            return arr[0];
        } else {
            var result = [];
            var rest = this.permute(arr.slice(1));
            for (var i = 0; i < rest.length; i++) {
                for (var j = 0; j < arr[0].length; j++) {
                    result.push([arr[0][j]].concat(rest[i]));
                }
            }
            return result;
        }
      },
      bubbleSelectors: function (selectors) {
        this.rules = [new(tree.Ruleset)(selectors.slice(0), [this.rules[0]])];
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.mixin = {};
  tree.mixin.Call = function (elements, args, index, currentFileInfo, important) {
      this.selector = new(tree.Selector)(elements);
      this.arguments = (args && args.length) ? args : null;
      this.index = index;
      this.currentFileInfo = currentFileInfo;
      this.important = important;
  };
  tree.mixin.Call.prototype = {
      type: "MixinCall",
      accept: function (visitor) {
          if (this.selector) {
              this.selector = visitor.visit(this.selector);
          }
          if (this.arguments) {
              this.arguments = visitor.visitArray(this.arguments);
          }
      },
      eval: function (env) {
          var mixins, mixin, args, rules = [], match = false, i, m, f, isRecursive, isOneFound, rule,
              candidates = [], candidate, conditionResult = [], defaultFunc = tree.defaultFunc,
              defaultResult, defNone = 0, defTrue = 1, defFalse = 2, count; 
  
          args = this.arguments && this.arguments.map(function (a) {
              return { name: a.name, value: a.value.eval(env) };
          });
  
          for (i = 0; i < env.frames.length; i++) {
              if ((mixins = env.frames[i].find(this.selector)).length > 0) {
                  isOneFound = true;
                  
                  // To make `default()` function independent of definition order we have two "subpasses" here.
                  // At first we evaluate each guard *twice* (with `default() == true` and `default() == false`),
                  // and build candidate list with corresponding flags. Then, when we know all possible matches,
                  // we make a final decision.
                  
                  for (m = 0; m < mixins.length; m++) {
                      mixin = mixins[m];
                      isRecursive = false;
                      for(f = 0; f < env.frames.length; f++) {
                          if ((!(mixin instanceof tree.mixin.Definition)) && mixin === (env.frames[f].originalRuleset || env.frames[f])) {
                              isRecursive = true;
                              break;
                          }
                      }
                      if (isRecursive) {
                          continue;
                      }
                      
                      if (mixin.matchArgs(args, env)) {  
                          candidate = {mixin: mixin, group: defNone};
                          
                          if (mixin.matchCondition) { 
                              for (f = 0; f < 2; f++) {
                                  defaultFunc.value(f);
                                  conditionResult[f] = mixin.matchCondition(args, env);
                              }
                              if (conditionResult[0] || conditionResult[1]) {
                                  if (conditionResult[0] != conditionResult[1]) {
                                      candidate.group = conditionResult[1] ?
                                          defTrue : defFalse;
                                  }
  
                                  candidates.push(candidate);
                              }   
                          }
                          else {
                              candidates.push(candidate);
                          }
                          
                          match = true;
                      }
                  }
                  
                  defaultFunc.reset();
  
                  count = [0, 0, 0];
                  for (m = 0; m < candidates.length; m++) {
                      count[candidates[m].group]++;
                  }
  
                  if (count[defNone] > 0) {
                      defaultResult = defFalse;
                  } else {
                      defaultResult = defTrue;
                      if ((count[defTrue] + count[defFalse]) > 1) {
                          throw { type: 'Runtime',
                              message: 'Ambiguous use of `default()` found when matching for `'
                                  + this.format(args) + '`',
                              index: this.index, filename: this.currentFileInfo.filename };
                      }
                  }
                  
                  for (m = 0; m < candidates.length; m++) {
                      candidate = candidates[m].group;
                      if ((candidate === defNone) || (candidate === defaultResult)) {
                          try {
                              mixin = candidates[m].mixin;
                              if (!(mixin instanceof tree.mixin.Definition)) {
                                  mixin = new tree.mixin.Definition("", [], mixin.rules, null, false);
                                  mixin.originalRuleset = mixins[m].originalRuleset || mixins[m];
                              }
                              Array.prototype.push.apply(
                                    rules, mixin.eval(env, args, this.important).rules);
                          } catch (e) {
                              throw { message: e.message, index: this.index, filename: this.currentFileInfo.filename, stack: e.stack };
                          }
                      }
                  }
                  
                  if (match) {
                      if (!this.currentFileInfo || !this.currentFileInfo.reference) {
                          for (i = 0; i < rules.length; i++) {
                              rule = rules[i];
                              if (rule.markReferenced) {
                                  rule.markReferenced();
                              }
                          }
                      }
                      return rules;
                  }
              }
          }
          if (isOneFound) {
              throw { type:    'Runtime',
                      message: 'No matching definition was found for `' + this.format(args) + '`',
                      index:   this.index, filename: this.currentFileInfo.filename };
          } else {
              throw { type:    'Name',
                      message: this.selector.toCSS().trim() + " is undefined",
                      index:   this.index, filename: this.currentFileInfo.filename };
          }
      },
      format: function (args) {
          return this.selector.toCSS().trim() + '(' +
              (args ? args.map(function (a) {
                  var argValue = "";
                  if (a.name) {
                      argValue += a.name + ":";
                  }
                  if (a.value.toCSS) {
                      argValue += a.value.toCSS();
                  } else {
                      argValue += "???";
                  }
                  return argValue;
              }).join(', ') : "") + ")";
      }
  };
  
  tree.mixin.Definition = function (name, params, rules, condition, variadic) {
      this.name = name;
      this.selectors = [new(tree.Selector)([new(tree.Element)(null, name, this.index, this.currentFileInfo)])];
      this.params = params;
      this.condition = condition;
      this.variadic = variadic;
      this.arity = params.length;
      this.rules = rules;
      this._lookups = {};
      this.required = params.reduce(function (count, p) {
          if (!p.name || (p.name && !p.value)) { return count + 1; }
          else                                 { return count; }
      }, 0);
      this.parent = tree.Ruleset.prototype;
      this.frames = [];
  };
  tree.mixin.Definition.prototype = {
      type: "MixinDefinition",
      accept: function (visitor) {
          if (this.params && this.params.length) {
              this.params = visitor.visitArray(this.params);
          }
          this.rules = visitor.visitArray(this.rules);
          if (this.condition) {
              this.condition = visitor.visit(this.condition);
          }
      },
      variable:  function (name) { return this.parent.variable.call(this, name); },
      variables: function ()     { return this.parent.variables.call(this); },
      find:      function ()     { return this.parent.find.apply(this, arguments); },
      rulesets:  function ()     { return this.parent.rulesets.apply(this); },
  
      evalParams: function (env, mixinEnv, args, evaldArguments) {
          /*jshint boss:true */
          var frame = new(tree.Ruleset)(null, null),
              varargs, arg,
              params = this.params.slice(0),
              i, j, val, name, isNamedFound, argIndex;
  
          mixinEnv = new tree.evalEnv(mixinEnv, [frame].concat(mixinEnv.frames));
  
          if (args) {
              args = args.slice(0);
  
              for(i = 0; i < args.length; i++) {
                  arg = args[i];
                  if (name = (arg && arg.name)) {
                      isNamedFound = false;
                      for(j = 0; j < params.length; j++) {
                          if (!evaldArguments[j] && name === params[j].name) {
                              evaldArguments[j] = arg.value.eval(env);
                              frame.prependRule(new(tree.Rule)(name, arg.value.eval(env)));
                              isNamedFound = true;
                              break;
                          }
                      }
                      if (isNamedFound) {
                          args.splice(i, 1);
                          i--;
                          continue;
                      } else {
                          throw { type: 'Runtime', message: "Named argument for " + this.name +
                              ' ' + args[i].name + ' not found' };
                      }
                  }
              }
          }
          argIndex = 0;
          for (i = 0; i < params.length; i++) {
              if (evaldArguments[i]) { continue; }
  
              arg = args && args[argIndex];
  
              if (name = params[i].name) {
                  if (params[i].variadic && args) {
                      varargs = [];
                      for (j = argIndex; j < args.length; j++) {
                          varargs.push(args[j].value.eval(env));
                      }
                      frame.prependRule(new(tree.Rule)(name, new(tree.Expression)(varargs).eval(env)));
                  } else {
                      val = arg && arg.value;
                      if (val) {
                          val = val.eval(env);
                      } else if (params[i].value) {
                          val = params[i].value.eval(mixinEnv);
                          frame.resetCache();
                      } else {
                          throw { type: 'Runtime', message: "wrong number of arguments for " + this.name +
                              ' (' + args.length + ' for ' + this.arity + ')' };
                      }
                      
                      frame.prependRule(new(tree.Rule)(name, val));
                      evaldArguments[i] = val;
                  }
              }
  
              if (params[i].variadic && args) {
                  for (j = argIndex; j < args.length; j++) {
                      evaldArguments[j] = args[j].value.eval(env);
                  }
              }
              argIndex++;
          }
  
          return frame;
      },
      eval: function (env, args, important) {
          var _arguments = [],
              mixinFrames = this.frames.concat(env.frames),
              frame = this.evalParams(env, new(tree.evalEnv)(env, mixinFrames), args, _arguments),
              rules, ruleset;
  
          frame.prependRule(new(tree.Rule)('@arguments', new(tree.Expression)(_arguments).eval(env)));
  
          rules = this.rules.slice(0);
  
          ruleset = new(tree.Ruleset)(null, rules);
          ruleset.originalRuleset = this;
          ruleset = ruleset.eval(new(tree.evalEnv)(env, [this, frame].concat(mixinFrames)));
          if (important) {
              ruleset = this.parent.makeImportant.apply(ruleset);
          }
          return ruleset;
      },
      matchCondition: function (args, env) {
          if (this.condition && !this.condition.eval(
              new(tree.evalEnv)(env,
                  [this.evalParams(env, new(tree.evalEnv)(env, this.frames.concat(env.frames)), args, [])] // the parameter variables
                      .concat(this.frames) // the parent namespace/mixin frames
                      .concat(env.frames)))) { // the current environment frames
              return false;
          }
          return true;
      },
      matchArgs: function (args, env) {
          var argsLength = (args && args.length) || 0, len;
  
          if (! this.variadic) {
              if (argsLength < this.required)                               { return false; }
              if (argsLength > this.params.length)                          { return false; }
          } else {
              if (argsLength < (this.required - 1))                         { return false; }
          }
  
          len = Math.min(argsLength, this.arity);
  
          for (var i = 0; i < len; i++) {
              if (!this.params[i].name && !this.params[i].variadic) {
                  if (args[i].value.eval(env).toCSS() != this.params[i].value.eval(env).toCSS()) {
                      return false;
                  }
              }
          }
          return true;
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Negative = function (node) {
      this.value = node;
  };
  tree.Negative.prototype = {
      type: "Negative",
      accept: function (visitor) {
          this.value = visitor.visit(this.value);
      },
      genCSS: function (env, output) {
          output.add('-');
          this.value.genCSS(env, output);
      },
      toCSS: tree.toCSS,
      eval: function (env) {
          if (env.isMathOn()) {
              return (new(tree.Operation)('*', [new(tree.Dimension)(-1), this.value])).eval(env);
          }
          return new(tree.Negative)(this.value.eval(env));
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Operation = function (op, operands, isSpaced) {
      this.op = op.trim();
      this.operands = operands;
      this.isSpaced = isSpaced;
  };
  tree.Operation.prototype = {
      type: "Operation",
      accept: function (visitor) {
          this.operands = visitor.visit(this.operands);
      },
      eval: function (env) {
          var a = this.operands[0].eval(env),
              b = this.operands[1].eval(env);
  
          if (env.isMathOn()) {
              if (a instanceof tree.Dimension && b instanceof tree.Color) {
                  a = a.toColor();
              }
              if (b instanceof tree.Dimension && a instanceof tree.Color) {
                  b = b.toColor();
              }
              if (!a.operate) {
                  throw { type: "Operation",
                          message: "Operation on an invalid type" };
              }
  
              return a.operate(env, this.op, b);
          } else {
              return new(tree.Operation)(this.op, [a, b], this.isSpaced);
          }
      },
      genCSS: function (env, output) {
          this.operands[0].genCSS(env, output);
          if (this.isSpaced) {
              output.add(" ");
          }
          output.add(this.op);
          if (this.isSpaced) {
              output.add(" ");
          }
          this.operands[1].genCSS(env, output);
      },
      toCSS: tree.toCSS
  };
  
  tree.operate = function (env, op, a, b) {
      switch (op) {
          case '+': return a + b;
          case '-': return a - b;
          case '*': return a * b;
          case '/': return a / b;
      }
  };
  
  })(require('../tree'));
  
  
  (function (tree) {
  
  tree.Paren = function (node) {
      this.value = node;
  };
  tree.Paren.prototype = {
      type: "Paren",
      accept: function (visitor) {
          this.value = visitor.visit(this.value);
      },
      genCSS: function (env, output) {
          output.add('(');
          this.value.genCSS(env, output);
          output.add(')');
      },
      toCSS: tree.toCSS,
      eval: function (env) {
          return new(tree.Paren)(this.value.eval(env));
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Quoted = function (str, content, escaped, index, currentFileInfo) {
      this.escaped = escaped;
      this.value = content || '';
      this.quote = str.charAt(0);
      this.index = index;
      this.currentFileInfo = currentFileInfo;
  };
  tree.Quoted.prototype = {
      type: "Quoted",
      genCSS: function (env, output) {
          if (!this.escaped) {
              output.add(this.quote, this.currentFileInfo, this.index);
          }
          output.add(this.value);
          if (!this.escaped) {
              output.add(this.quote);
          }
      },
      toCSS: tree.toCSS,
      eval: function (env) {
          var that = this;
          var value = this.value.replace(/`([^`]+)`/g, function (_, exp) {
              return new(tree.JavaScript)(exp, that.index, true).eval(env).value;
          }).replace(/@\{([\w-]+)\}/g, function (_, name) {
              var v = new(tree.Variable)('@' + name, that.index, that.currentFileInfo).eval(env, true);
              return (v instanceof tree.Quoted) ? v.value : v.toCSS();
          });
          return new(tree.Quoted)(this.quote + value + this.quote, value, this.escaped, this.index, this.currentFileInfo);
      },
      compare: function (x) {
          if (!x.toCSS) {
              return -1;
          }
          
          var left = this.toCSS(),
              right = x.toCSS();
          
          if (left === right) {
              return 0;
          }
          
          return left < right ? -1 : 1;
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Rule = function (name, value, important, merge, index, currentFileInfo, inline) {
      this.name = name;
      this.value = (value instanceof tree.Value) ? value : new(tree.Value)([value]);
      this.important = important ? ' ' + important.trim() : '';
      this.merge = merge;
      this.index = index;
      this.currentFileInfo = currentFileInfo;
      this.inline = inline || false;
      this.variable = name.charAt && (name.charAt(0) === '@');
  };
  
  tree.Rule.prototype = {
      type: "Rule",
      accept: function (visitor) {
          this.value = visitor.visit(this.value);
      },
      genCSS: function (env, output) {
          output.add(this.name + (env.compress ? ':' : ': '), this.currentFileInfo, this.index);
          try {
              this.value.genCSS(env, output);
          }
          catch(e) {
              e.index = this.index;
              e.filename = this.currentFileInfo.filename;
              throw e;
          }
          output.add(this.important + ((this.inline || (env.lastRule && env.compress)) ? "" : ";"), this.currentFileInfo, this.index);
      },
      toCSS: tree.toCSS,
      eval: function (env) {
          var strictMathBypass = false, name = this.name;    
          if (typeof name !== "string") {
              // expand 'primitive' name directly to get
              // things faster (~10% for benchmark.less):
              name = (name.length === 1) 
                  && (name[0] instanceof tree.Keyword)
                      ? name[0].value : evalName(env, name);
          }
          if (name === "font" && !env.strictMath) {
              strictMathBypass = true;
              env.strictMath = true;
          }
          try {
              return new(tree.Rule)(name,
                                this.value.eval(env),
                                this.important,
                                this.merge,
                                this.index, this.currentFileInfo, this.inline);
          }
          catch(e) {
              e.index = e.index || this.index;
              throw e;
          }
          finally {
              if (strictMathBypass) {
                  env.strictMath = false;
              }
          }
      },
      makeImportant: function () {
          return new(tree.Rule)(this.name,
                                this.value,
                                "!important",
                                this.merge,
                                this.index, this.currentFileInfo, this.inline);
      }
  };
  
  function evalName(env, name) {
      var value = "", i, n = name.length,
          output = {add: function (s) {value += s;}};
      for (i = 0; i < n; i++) {
          name[i].eval(env).genCSS(env, output);
      }
      return value;
  }
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Ruleset = function (selectors, rules, strictImports) {
      this.selectors = selectors;
      this.rules = rules;
      this._lookups = {};
      this.strictImports = strictImports;
  };
  tree.Ruleset.prototype = {
      type: "Ruleset",
      accept: function (visitor) {
          if (this.paths) {
              visitor.visitArray(this.paths, true);
          } else if (this.selectors) {
              this.selectors = visitor.visitArray(this.selectors);
          }
          if (this.rules && this.rules.length) {
              this.rules = visitor.visitArray(this.rules);
          }
      },
      eval: function (env) {
          var thisSelectors = this.selectors, selectors, 
              selCnt, i, defaultFunc = tree.defaultFunc;
          if (thisSelectors && (selCnt = thisSelectors.length)) {
              selectors = [];
              defaultFunc.error({
                  type: "Syntax", 
                  message: "it is currently only allowed in parametric mixin guards," 
              });
              for (i = 0; i < selCnt; i++) {
                  selectors.push(thisSelectors[i].eval(env));
              }
              defaultFunc.reset();  
          }
  
          var rules = this.rules ? this.rules.slice(0) : null,
              ruleset = new(tree.Ruleset)(selectors, rules, this.strictImports),
              rule, subRule;
  
          ruleset.originalRuleset = this;
          ruleset.root = this.root;
          ruleset.firstRoot = this.firstRoot;
          ruleset.allowImports = this.allowImports;
  
          if(this.debugInfo) {
              ruleset.debugInfo = this.debugInfo;
          }
  
          // push the current ruleset to the frames stack
          var envFrames = env.frames;
          envFrames.unshift(ruleset);
  
          // currrent selectors
          var envSelectors = env.selectors;
          if (!envSelectors) {
              env.selectors = envSelectors = [];
          }
          envSelectors.unshift(this.selectors);
  
          // Evaluate imports
          if (ruleset.root || ruleset.allowImports || !ruleset.strictImports) {
              ruleset.evalImports(env);
          }
  
          // Store the frames around mixin definitions,
          // so they can be evaluated like closures when the time comes.
          var rsRules = ruleset.rules, rsRuleCnt = rsRules ? rsRules.length : 0;
          for (i = 0; i < rsRuleCnt; i++) {
              if (rsRules[i] instanceof tree.mixin.Definition) {
                  rsRules[i].frames = envFrames.slice(0);
              }
          }
  
          var mediaBlockCount = (env.mediaBlocks && env.mediaBlocks.length) || 0;
  
          // Evaluate mixin calls.
          for (i = 0; i < rsRuleCnt; i++) {
              if (rsRules[i] instanceof tree.mixin.Call) {
                  /*jshint loopfunc:true */
                  rules = rsRules[i].eval(env).filter(function(r) {
                      if ((r instanceof tree.Rule) && r.variable) {
                          // do not pollute the scope if the variable is
                          // already there. consider returning false here
                          // but we need a way to "return" variable from mixins
                          return !(ruleset.variable(r.name));
                      }
                      return true;
                  });
                  rsRules.splice.apply(rsRules, [i, 1].concat(rules));
                  rsRuleCnt += rules.length - 1;
                  i += rules.length-1;
                  ruleset.resetCache();
              }
          }
  
          // Evaluate everything else
          for (i = 0; i < rsRules.length; i++) {
              rule = rsRules[i];
              if (! (rule instanceof tree.mixin.Definition)) {
                  rsRules[i] = rule = rule.eval ? rule.eval(env) : rule;
                  // for rulesets, check if it is a css guard and can be removed
                  if (rule instanceof tree.Ruleset && rule.selectors && rule.selectors.length === 1) {
                      // check if it can be folded in (e.g. & where)
                      if (rule.selectors[0].isJustParentSelector()) {
                          rsRules.splice(i--, 1);
                          // cannot call if there is no selector, so we can just continue
                          if (!rule.selectors[0].evaldCondition) {
                              continue;
                          }
                          for(var j = 0; j < rule.rules.length; j++) {
                              subRule = rule.rules[j];
                              if (!(subRule instanceof tree.Rule) || !subRule.variable) {
                                  rsRules.splice(++i, 0, subRule);
                              }
                          }
                      }
                  }
              }
          }
  
          // Pop the stack
          envFrames.shift();
          envSelectors.shift();
          
          if (env.mediaBlocks) {
              for (i = mediaBlockCount; i < env.mediaBlocks.length; i++) {
                  env.mediaBlocks[i].bubbleSelectors(selectors);
              }
          }
  
          return ruleset;
      },
      evalImports: function(env) {
          var rules = this.rules, i, importRules;
          if (!rules) { return; }
  
          for (i = 0; i < rules.length; i++) {
              if (rules[i] instanceof tree.Import) {
                  importRules = rules[i].eval(env);
                  if (importRules && importRules.length) {
                      rules.splice.apply(rules, [i, 1].concat(importRules));
                      i+= importRules.length-1;
                  } else {
                      rules.splice(i, 1, importRules);
                  }
                  this.resetCache();
              }
          }
      },
      makeImportant: function() {
          return new tree.Ruleset(this.selectors, this.rules.map(function (r) {
                      if (r.makeImportant) {
                          return r.makeImportant();
                      } else {
                          return r;
                      }
                  }), this.strictImports);
      },
      matchArgs: function (args) {
          return !args || args.length === 0;
      },
      // lets you call a css selector with a guard
      matchCondition: function (args, env) {
          var lastSelector = this.selectors[this.selectors.length-1];
          if (!lastSelector.evaldCondition) {
              return false;
          }
          if (lastSelector.condition &&
              !lastSelector.condition.eval(
                  new(tree.evalEnv)(env,
                      env.frames))) {
              return false;
          }
          return true;
      },
      resetCache: function () {
          this._rulesets = null;
          this._variables = null;
          this._lookups = {};
      },
      variables: function () {
          if (!this._variables) {
              this._variables = !this.rules ? {} : this.rules.reduce(function (hash, r) {
                  if (r instanceof tree.Rule && r.variable === true) {
                      hash[r.name] = r;
                  }
                  return hash;
              }, {});
          }
          return this._variables;
      },
      variable: function (name) {
          return this.variables()[name];
      },
      rulesets: function () {
          if (!this.rules) { return null; }
  
          var _Ruleset = tree.Ruleset, _MixinDefinition = tree.mixin.Definition,
              filtRules = [], rules = this.rules, cnt = rules.length,
              i, rule;
  
          for (i = 0; i < cnt; i++) {
              rule = rules[i];
              if ((rule instanceof _Ruleset) || (rule instanceof _MixinDefinition)) {
                  filtRules.push(rule);
              }
          }
  
          return filtRules;
      },
      prependRule: function (rule) {
          var rules = this.rules;
          if (rules) { rules.unshift(rule); } else { this.rules = [ rule ]; }
      },
      find: function (selector, self) {
          self = self || this;
          var rules = [], match,
              key = selector.toCSS();
  
          if (key in this._lookups) { return this._lookups[key]; }
  
          this.rulesets().forEach(function (rule) {
              if (rule !== self) {
                  for (var j = 0; j < rule.selectors.length; j++) {
                      match = selector.match(rule.selectors[j]);
                      if (match) {
                          if (selector.elements.length > match) {
                              Array.prototype.push.apply(rules, rule.find(
                                  new(tree.Selector)(selector.elements.slice(match)), self));
                          } else {
                              rules.push(rule);
                          }
                          break;
                      }
                  }
              }
          });
          this._lookups[key] = rules;
          return rules;
      },
      genCSS: function (env, output) {
          var i, j,
              ruleNodes = [],
              rulesetNodes = [],
              rulesetNodeCnt,
              debugInfo,     // Line number debugging
              rule,
              path;
  
          env.tabLevel = (env.tabLevel || 0);
  
          if (!this.root) {
              env.tabLevel++;
          }
  
          var tabRuleStr = env.compress ? '' : Array(env.tabLevel + 1).join("  "),
              tabSetStr = env.compress ? '' : Array(env.tabLevel).join("  "),
              sep;
  
          for (i = 0; i < this.rules.length; i++) {
              rule = this.rules[i];
              if (rule.rules || (rule instanceof tree.Media) || rule instanceof tree.Directive || (this.root && rule instanceof tree.Comment)) {
                  rulesetNodes.push(rule);
              } else {
                  ruleNodes.push(rule);
              }
          }
  
          // If this is the root node, we don't render
          // a selector, or {}.
          if (!this.root) {
              debugInfo = tree.debugInfo(env, this, tabSetStr);
  
              if (debugInfo) {
                  output.add(debugInfo);
                  output.add(tabSetStr);
              }
  
              var paths = this.paths, pathCnt = paths.length,
                  pathSubCnt;
  
              sep = env.compress ? ',' : (',\n' + tabSetStr);
  
              for (i = 0; i < pathCnt; i++) {
                  path = paths[i];
                  if (!(pathSubCnt = path.length)) { continue; }
                  if (i > 0) { output.add(sep); }
  
                  env.firstSelector = true;
                  path[0].genCSS(env, output);
  
                  env.firstSelector = false;
                  for (j = 1; j < pathSubCnt; j++) {
                      path[j].genCSS(env, output);
                  }
              }
  
              output.add((env.compress ? '{' : ' {\n') + tabRuleStr);
          }
  
          // Compile rules and rulesets
          for (i = 0; i < ruleNodes.length; i++) {
              rule = ruleNodes[i];
  
              // @page{ directive ends up with root elements inside it, a mix of rules and rulesets
              // In this instance we do not know whether it is the last property
              if (i + 1 === ruleNodes.length && (!this.root || rulesetNodes.length === 0 || this.firstRoot)) {
                  env.lastRule = true;
              }
  
              if (rule.genCSS) {
                  rule.genCSS(env, output);
              } else if (rule.value) {
                  output.add(rule.value.toString());
              }
  
              if (!env.lastRule) {
                  output.add(env.compress ? '' : ('\n' + tabRuleStr));
              } else {
                  env.lastRule = false;
              }
          }
  
          if (!this.root) {
              output.add((env.compress ? '}' : '\n' + tabSetStr + '}'));
              env.tabLevel--;
          }
  
          sep = (env.compress ? "" : "\n") + (this.root ? tabRuleStr : tabSetStr);
          rulesetNodeCnt = rulesetNodes.length;
          if (rulesetNodeCnt) {
              if (ruleNodes.length && sep) { output.add(sep); }
              rulesetNodes[0].genCSS(env, output);
              for (i = 1; i < rulesetNodeCnt; i++) {
                  if (sep) { output.add(sep); }
                  rulesetNodes[i].genCSS(env, output);
              }
          }
  
          if (!output.isEmpty() && !env.compress && this.firstRoot) {
              output.add('\n');
          }
      },
  
      toCSS: tree.toCSS,
  
      markReferenced: function () {
          for (var s = 0; s < this.selectors.length; s++) {
              this.selectors[s].markReferenced();
          }
      },
  
      joinSelectors: function (paths, context, selectors) {
          for (var s = 0; s < selectors.length; s++) {
              this.joinSelector(paths, context, selectors[s]);
          }
      },
  
      joinSelector: function (paths, context, selector) {
  
          var i, j, k, 
              hasParentSelector, newSelectors, el, sel, parentSel, 
              newSelectorPath, afterParentJoin, newJoinedSelector, 
              newJoinedSelectorEmpty, lastSelector, currentElements,
              selectorsMultiplied;
      
          for (i = 0; i < selector.elements.length; i++) {
              el = selector.elements[i];
              if (el.value === '&') {
                  hasParentSelector = true;
              }
          }
      
          if (!hasParentSelector) {
              if (context.length > 0) {
                  for (i = 0; i < context.length; i++) {
                      paths.push(context[i].concat(selector));
                  }
              }
              else {
                  paths.push([selector]);
              }
              return;
          }
  
          // The paths are [[Selector]]
          // The first list is a list of comma seperated selectors
          // The inner list is a list of inheritance seperated selectors
          // e.g.
          // .a, .b {
          //   .c {
          //   }
          // }
          // == [[.a] [.c]] [[.b] [.c]]
          //
  
          // the elements from the current selector so far
          currentElements = [];
          // the current list of new selectors to add to the path.
          // We will build it up. We initiate it with one empty selector as we "multiply" the new selectors
          // by the parents
          newSelectors = [[]];
  
          for (i = 0; i < selector.elements.length; i++) {
              el = selector.elements[i];
              // non parent reference elements just get added
              if (el.value !== "&") {
                  currentElements.push(el);
              } else {
                  // the new list of selectors to add
                  selectorsMultiplied = [];
  
                  // merge the current list of non parent selector elements
                  // on to the current list of selectors to add
                  if (currentElements.length > 0) {
                      this.mergeElementsOnToSelectors(currentElements, newSelectors);
                  }
  
                  // loop through our current selectors
                  for (j = 0; j < newSelectors.length; j++) {
                      sel = newSelectors[j];
                      // if we don't have any parent paths, the & might be in a mixin so that it can be used
                      // whether there are parents or not
                      if (context.length === 0) {
                          // the combinator used on el should now be applied to the next element instead so that
                          // it is not lost
                          if (sel.length > 0) {
                              sel[0].elements = sel[0].elements.slice(0);
                              sel[0].elements.push(new(tree.Element)(el.combinator, '', el.index, el.currentFileInfo));
                          }
                          selectorsMultiplied.push(sel);
                      }
                      else {
                          // and the parent selectors
                          for (k = 0; k < context.length; k++) {
                              parentSel = context[k];
                              // We need to put the current selectors
                              // then join the last selector's elements on to the parents selectors
  
                              // our new selector path
                              newSelectorPath = [];
                              // selectors from the parent after the join
                              afterParentJoin = [];
                              newJoinedSelectorEmpty = true;
  
                              //construct the joined selector - if & is the first thing this will be empty,
                              // if not newJoinedSelector will be the last set of elements in the selector
                              if (sel.length > 0) {
                                  newSelectorPath = sel.slice(0);
                                  lastSelector = newSelectorPath.pop();
                                  newJoinedSelector = selector.createDerived(lastSelector.elements.slice(0));
                                  newJoinedSelectorEmpty = false;
                              }
                              else {
                                  newJoinedSelector = selector.createDerived([]);
                              }
  
                              //put together the parent selectors after the join
                              if (parentSel.length > 1) {
                                  afterParentJoin = afterParentJoin.concat(parentSel.slice(1));
                              }
  
                              if (parentSel.length > 0) {
                                  newJoinedSelectorEmpty = false;
  
                                  // join the elements so far with the first part of the parent
                                  newJoinedSelector.elements.push(new(tree.Element)(el.combinator, parentSel[0].elements[0].value, el.index, el.currentFileInfo));
                                  newJoinedSelector.elements = newJoinedSelector.elements.concat(parentSel[0].elements.slice(1));
                              }
  
                              if (!newJoinedSelectorEmpty) {
                                  // now add the joined selector
                                  newSelectorPath.push(newJoinedSelector);
                              }
  
                              // and the rest of the parent
                              newSelectorPath = newSelectorPath.concat(afterParentJoin);
  
                              // add that to our new set of selectors
                              selectorsMultiplied.push(newSelectorPath);
                          }
                      }
                  }
  
                  // our new selectors has been multiplied, so reset the state
                  newSelectors = selectorsMultiplied;
                  currentElements = [];
              }
          }
  
          // if we have any elements left over (e.g. .a& .b == .b)
          // add them on to all the current selectors
          if (currentElements.length > 0) {
              this.mergeElementsOnToSelectors(currentElements, newSelectors);
          }
  
          for (i = 0; i < newSelectors.length; i++) {
              if (newSelectors[i].length > 0) {
                  paths.push(newSelectors[i]);
              }
          }
      },
      
      mergeElementsOnToSelectors: function(elements, selectors) {
          var i, sel;
  
          if (selectors.length === 0) {
              selectors.push([ new(tree.Selector)(elements) ]);
              return;
          }
  
          for (i = 0; i < selectors.length; i++) {
              sel = selectors[i];
  
              // if the previous thing in sel is a parent this needs to join on to it
              if (sel.length > 0) {
                  sel[sel.length - 1] = sel[sel.length - 1].createDerived(sel[sel.length - 1].elements.concat(elements));
              }
              else {
                  sel.push(new(tree.Selector)(elements));
              }
          }
      }
  };
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Selector = function (elements, extendList, condition, index, currentFileInfo, isReferenced) {
      this.elements = elements;
      this.extendList = extendList;
      this.condition = condition;
      this.currentFileInfo = currentFileInfo || {};
      this.isReferenced = isReferenced;
      if (!condition) {
          this.evaldCondition = true;
      }
  };
  tree.Selector.prototype = {
      type: "Selector",
      accept: function (visitor) {
          if (this.elements) {
              this.elements = visitor.visitArray(this.elements);
          }
          if (this.extendList) {
              this.extendList = visitor.visitArray(this.extendList);
          }
          if (this.condition) {
              this.condition = visitor.visit(this.condition);
          }
      },
      createDerived: function(elements, extendList, evaldCondition) {
          evaldCondition = (evaldCondition != null) ? evaldCondition : this.evaldCondition;
          var newSelector = new(tree.Selector)(elements, extendList || this.extendList, null, this.index, this.currentFileInfo, this.isReferenced);
          newSelector.evaldCondition = evaldCondition;
          newSelector.mediaEmpty = this.mediaEmpty;
          return newSelector;
      },
      match: function (other) {
          var elements = this.elements,
              len = elements.length,
              olen, i;
  
          other.CacheElements();
  
          olen = other._elements.length;
          if (olen === 0 || len < olen) {
              return 0;
          } else {
              for (i = 0; i < olen; i++) {
                  if (elements[i].value !== other._elements[i]) {
                      return 0;
                  }
              }
          }
  
          return olen; // return number of matched elements
      },
      CacheElements: function(){
          var css = '', len, v, i;
  
          if( !this._elements ){
  
              len = this.elements.length;
              for(i = 0; i < len; i++){
  
                  v = this.elements[i];
                  css += v.combinator.value;
  
                  if( !v.value.value ){
                      css += v.value;
                      continue;
                  }
  
                  if( typeof v.value.value !== "string" ){
                      css = '';
                      break;
                  }
                  css += v.value.value;
              }
  
              this._elements = css.match(/[,&#\.\w-]([\w-]|(\\.))*/g);
  
              if (this._elements) {
                  if (this._elements[0] === "&") {
                      this._elements.shift();
                  }
  
              } else {
                  this._elements = [];
              }
  
          }
      },
      isJustParentSelector: function() {
          return !this.mediaEmpty && 
              this.elements.length === 1 && 
              this.elements[0].value === '&' && 
              (this.elements[0].combinator.value === ' ' || this.elements[0].combinator.value === '');
      },
      eval: function (env) {
          var evaldCondition = this.condition && this.condition.eval(env),
              elements = this.elements, extendList = this.extendList;
  
          elements = elements && elements.map(function (e) { return e.eval(env); });
          extendList = extendList && extendList.map(function(extend) { return extend.eval(env); });
  
          return this.createDerived(elements, extendList, evaldCondition);
      },
      genCSS: function (env, output) {
          var i, element;
          if ((!env || !env.firstSelector) && this.elements[0].combinator.value === "") {
              output.add(' ', this.currentFileInfo, this.index);
          }
          if (!this._css) {
              //TODO caching? speed comparison?
              for(i = 0; i < this.elements.length; i++) {
                  element = this.elements[i];
                  element.genCSS(env, output);
              }
          }
      },
      toCSS: tree.toCSS,
      markReferenced: function () {
          this.isReferenced = true;
      },
      getIsReferenced: function() {
          return !this.currentFileInfo.reference || this.isReferenced;
      },
      getIsOutput: function() {
          return this.evaldCondition;
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.UnicodeDescriptor = function (value) {
      this.value = value;
  };
  tree.UnicodeDescriptor.prototype = {
      type: "UnicodeDescriptor",
      genCSS: function (env, output) {
          output.add(this.value);
      },
      toCSS: tree.toCSS,
      eval: function () { return this; }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.URL = function (val, currentFileInfo, isEvald) {
      this.value = val;
      this.currentFileInfo = currentFileInfo;
      this.isEvald = isEvald;
  };
  tree.URL.prototype = {
      type: "Url",
      accept: function (visitor) {
          this.value = visitor.visit(this.value);
      },
      genCSS: function (env, output) {
          output.add("url(");
          this.value.genCSS(env, output);
          output.add(")");
      },
      toCSS: tree.toCSS,
      eval: function (ctx) {
          var val = this.value.eval(ctx),
              rootpath;
  
          if (!this.isEvald) {
              // Add the base path if the URL is relative
              rootpath = this.currentFileInfo && this.currentFileInfo.rootpath;
              if (rootpath && typeof val.value === "string" && ctx.isPathRelative(val.value)) {
                  if (!val.quote) {
                      rootpath = rootpath.replace(/[\(\)'"\s]/g, function(match) { return "\\"+match; });
                  }
                  val.value = rootpath + val.value;
              }
              
              val.value = ctx.normalizePath(val.value);
  
              // Add url args if enabled
              if (ctx.urlArgs) {
                  if (!val.value.match(/^\s*data:/)) {
                      var delimiter = val.value.indexOf('?') === -1 ? '?' : '&';
                      var urlArgs = delimiter + ctx.urlArgs;
                      if (val.value.indexOf('#') !== -1) {
                          val.value = val.value.replace('#', urlArgs + '#');
                      } else {
                          val.value += urlArgs;
                      }
                  }
              }
          }
  
          return new(tree.URL)(val, this.currentFileInfo, true);
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Value = function (value) {
      this.value = value;
  };
  tree.Value.prototype = {
      type: "Value",
      accept: function (visitor) {
          if (this.value) {
              this.value = visitor.visitArray(this.value);
          }
      },
      eval: function (env) {
          if (this.value.length === 1) {
              return this.value[0].eval(env);
          } else {
              return new(tree.Value)(this.value.map(function (v) {
                  return v.eval(env);
              }));
          }
      },
      genCSS: function (env, output) {
          var i;
          for(i = 0; i < this.value.length; i++) {
              this.value[i].genCSS(env, output);
              if (i+1 < this.value.length) {
                  output.add((env && env.compress) ? ',' : ', ');
              }
          }
      },
      toCSS: tree.toCSS
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
  tree.Variable = function (name, index, currentFileInfo) {
      this.name = name;
      this.index = index;
      this.currentFileInfo = currentFileInfo || {};
  };
  tree.Variable.prototype = {
      type: "Variable",
      eval: function (env) {
          var variable, name = this.name;
  
          if (name.indexOf('@@') === 0) {
              name = '@' + new(tree.Variable)(name.slice(1)).eval(env).value;
          }
          
          if (this.evaluating) {
              throw { type: 'Name',
                      message: "Recursive variable definition for " + name,
                      filename: this.currentFileInfo.file,
                      index: this.index };
          }
          
          this.evaluating = true;
  
          variable = tree.find(env.frames, function (frame) {
              var v = frame.variable(name);
              if (v) {
                  return v.value.eval(env);
              }
          });
          if (variable) { 
              this.evaluating = false;
              return variable;
          } else {
              throw { type: 'Name',
                      message: "variable " + name + " is undefined",
                      filename: this.currentFileInfo.filename,
                      index: this.index };
          }
      }
  };
  
  })(require('../tree'));
  
  (function (tree) {
  
      var parseCopyProperties = [
          'paths',            // option - unmodified - paths to search for imports on
          'optimization',     // option - optimization level (for the chunker)
          'files',            // list of files that have been imported, used for import-once
          'contents',         // map - filename to contents of all the files
          'contentsIgnoredChars', // map - filename to lines at the begining of each file to ignore
          'relativeUrls',     // option - whether to adjust URL's to be relative
          'rootpath',         // option - rootpath to append to URL's
          'strictImports',    // option -
          'insecure',         // option - whether to allow imports from insecure ssl hosts
          'dumpLineNumbers',  // option - whether to dump line numbers
          'compress',         // option - whether to compress
          'processImports',   // option - whether to process imports. if false then imports will not be imported
          'syncImport',       // option - whether to import synchronously
          'javascriptEnabled',// option - whether JavaScript is enabled. if undefined, defaults to true
          'mime',             // browser only - mime type for sheet import
          'useFileCache',     // browser only - whether to use the per file session cache
          'currentFileInfo'   // information about the current file - for error reporting and importing and making urls relative etc.
      ];
  
      //currentFileInfo = {
      //  'relativeUrls' - option - whether to adjust URL's to be relative
      //  'filename' - full resolved filename of current file
      //  'rootpath' - path to append to normal URLs for this node
      //  'currentDirectory' - path to the current file, absolute
      //  'rootFilename' - filename of the base file
      //  'entryPath' - absolute path to the entry file
      //  'reference' - whether the file should not be output and only output parts that are referenced
  
      tree.parseEnv = function(options) {
          copyFromOriginal(options, this, parseCopyProperties);
  
          if (!this.contents) { this.contents = {}; }
          if (!this.contentsIgnoredChars) { this.contentsIgnoredChars = {}; }
          if (!this.files) { this.files = {}; }
  
          if (!this.currentFileInfo) {
              var filename = (options && options.filename) || "input";
              var entryPath = filename.replace(/[^\/\\]*$/, "");
              if (options) {
                  options.filename = null;
              }
              this.currentFileInfo = {
                  filename: filename,
                  relativeUrls: this.relativeUrls,
                  rootpath: (options && options.rootpath) || "",
                  currentDirectory: entryPath,
                  entryPath: entryPath,
                  rootFilename: filename
              };
          }
      };
  
      var evalCopyProperties = [
          'silent',         // whether to swallow errors and warnings
          'verbose',        // whether to log more activity
          'compress',       // whether to compress
          'yuicompress',    // whether to compress with the outside tool yui compressor
          'ieCompat',       // whether to enforce IE compatibility (IE8 data-uri)
          'strictMath',     // whether math has to be within parenthesis
          'strictUnits',    // whether units need to evaluate correctly
          'cleancss',       // whether to compress with clean-css
          'sourceMap',      // whether to output a source map
          'importMultiple', // whether we are currently importing multiple copies
          'urlArgs'         // whether to add args into url tokens
          ];
  
      tree.evalEnv = function(options, frames) {
          copyFromOriginal(options, this, evalCopyProperties);
  
          this.frames = frames || [];
      };
  
      tree.evalEnv.prototype.inParenthesis = function () {
          if (!this.parensStack) {
              this.parensStack = [];
          }
          this.parensStack.push(true);
      };
  
      tree.evalEnv.prototype.outOfParenthesis = function () {
          this.parensStack.pop();
      };
  
      tree.evalEnv.prototype.isMathOn = function () {
          return this.strictMath ? (this.parensStack && this.parensStack.length) : true;
      };
  
      tree.evalEnv.prototype.isPathRelative = function (path) {
          return !/^(?:[a-z-]+:|\/)/.test(path);
      };
  
      tree.evalEnv.prototype.normalizePath = function( path ) {
          var
            segments = path.split("/").reverse(),
            segment;
  
          path = [];
          while (segments.length !== 0 ) {
              segment = segments.pop();
              switch( segment ) {
                  case ".":
                      break;
                  case "..":
                      if ((path.length === 0) || (path[path.length - 1] === "..")) {
                          path.push( segment );
                      } else {
                          path.pop();
                      }
                      break;
                  default:
                      path.push( segment );
                      break;
              }
          }
  
          return path.join("/");
      };
  
      //todo - do the same for the toCSS env
      //tree.toCSSEnv = function (options) {
      //};
  
      var copyFromOriginal = function(original, destination, propertiesToCopy) {
          if (!original) { return; }
  
          for(var i = 0; i < propertiesToCopy.length; i++) {
              if (original.hasOwnProperty(propertiesToCopy[i])) {
                  destination[propertiesToCopy[i]] = original[propertiesToCopy[i]];
              }
          }
      };
  
  })(require('./tree'));
  
  (function (tree) {
  
      var _visitArgs = { visitDeeper: true },
          _hasIndexed = false;
  
      function _noop(node) {
          return node;
      }
  
      function indexNodeTypes(parent, ticker) {
          // add .typeIndex to tree node types for lookup table
          var key, child;
          for (key in parent) {
              if (parent.hasOwnProperty(key)) {
                  child = parent[key];
                  switch (typeof child) {
                      case "function":
                          // ignore bound functions directly on tree which do not have a prototype
                          // or aren't nodes
                          if (child.prototype && child.prototype.type) {
                              child.prototype.typeIndex = ticker++;
                          }
                          break;
                      case "object":
                          ticker = indexNodeTypes(child, ticker);
                          break;
                  }
              }
          }
          return ticker;
      }
  
      tree.visitor = function(implementation) {
          this._implementation = implementation;
          this._visitFnCache = [];
  
          if (!_hasIndexed) {
              indexNodeTypes(tree, 1);
              _hasIndexed = true;
          }
      };
  
      tree.visitor.prototype = {
          visit: function(node) {
              if (!node) {
                  return node;
              }
  
              var nodeTypeIndex = node.typeIndex;
              if (!nodeTypeIndex) {
                  return node;
              }
  
              var visitFnCache = this._visitFnCache,
                  impl = this._implementation,
                  aryIndx = nodeTypeIndex << 1,
                  outAryIndex = aryIndx | 1,
                  func = visitFnCache[aryIndx],
                  funcOut = visitFnCache[outAryIndex],
                  visitArgs = _visitArgs,
                  fnName;
  
              visitArgs.visitDeeper = true;
  
              if (!func) {
                  fnName = "visit" + node.type;
                  func = impl[fnName] || _noop;
                  funcOut = impl[fnName + "Out"] || _noop;
                  visitFnCache[aryIndx] = func;
                  visitFnCache[outAryIndex] = funcOut;
              }
  
              if (func !== _noop) {
                  var newNode = func.call(impl, node, visitArgs);
                  if (impl.isReplacing) {
                      node = newNode;
                  }
              }
  
              if (visitArgs.visitDeeper && node && node.accept) {
                  node.accept(this);
              }
  
              if (funcOut != _noop) {
                  funcOut.call(impl, node);
              }
  
              return node;
          },
          visitArray: function(nodes, nonReplacing) {
              if (!nodes) {
                  return nodes;
              }
  
              var cnt = nodes.length, i;
  
              // Non-replacing
              if (nonReplacing || !this._implementation.isReplacing) {
                  for (i = 0; i < cnt; i++) {
                      this.visit(nodes[i]);
                  }
                  return nodes;
              }
  
              // Replacing
              var out = [];
              for (i = 0; i < cnt; i++) {
                  var evald = this.visit(nodes[i]);
                  if (!evald.splice) {
                      out.push(evald);
                  } else if (evald.length) {
                      this.flatten(evald, out);
                  }
              }
              return out;
          },
          flatten: function(arr, out) {
              if (!out) {
                  out = [];
              }
  
              var cnt, i, item,
                  nestedCnt, j, nestedItem;
  
              for (i = 0, cnt = arr.length; i < cnt; i++) {
                  item = arr[i];
                  if (!item.splice) {
                      out.push(item);
                      continue;
                  }
  
                  for (j = 0, nestedCnt = item.length; j < nestedCnt; j++) {
                      nestedItem = item[j];
                      if (!nestedItem.splice) {
                          out.push(nestedItem);
                      } else if (nestedItem.length) {
                          this.flatten(nestedItem, out);
                      }
                  }
              }
  
              return out;
          }
      };
  
  })(require('./tree'));
  (function (tree) {
      tree.importVisitor = function(importer, finish, evalEnv) {
          this._visitor = new tree.visitor(this);
          this._importer = importer;
          this._finish = finish;
          this.env = evalEnv || new tree.evalEnv();
          this.importCount = 0;
      };
  
      tree.importVisitor.prototype = {
          isReplacing: true,
          run: function (root) {
              var error;
              try {
                  // process the contents
                  this._visitor.visit(root);
              }
              catch(e) {
                  error = e;
              }
  
              this.isFinished = true;
  
              if (this.importCount === 0) {
                  this._finish(error);
              }
          },
          visitImport: function (importNode, visitArgs) {
              var importVisitor = this,
                  evaldImportNode,
                  inlineCSS = importNode.options.inline;
              
              if (!importNode.css || inlineCSS) {
  
                  try {
                      evaldImportNode = importNode.evalForImport(this.env);
                  } catch(e){
                      if (!e.filename) { e.index = importNode.index; e.filename = importNode.currentFileInfo.filename; }
                      // attempt to eval properly and treat as css
                      importNode.css = true;
                      // if that fails, this error will be thrown
                      importNode.error = e;
                  }
  
                  if (evaldImportNode && (!evaldImportNode.css || inlineCSS)) {
                      importNode = evaldImportNode;
                      this.importCount++;
                      var env = new tree.evalEnv(this.env, this.env.frames.slice(0));
  
                      if (importNode.options.multiple) {
                          env.importMultiple = true;
                      }
  
                      this._importer.push(importNode.getPath(), importNode.currentFileInfo, importNode.options, function (e, root, imported, fullPath) {
                          if (e && !e.filename) { e.index = importNode.index; e.filename = importNode.currentFileInfo.filename; }
  
                          if (imported && !env.importMultiple) { importNode.skip = imported; }
  
                          var subFinish = function(e) {
                              importVisitor.importCount--;
  
                              if (importVisitor.importCount === 0 && importVisitor.isFinished) {
                                  importVisitor._finish(e);
                              }
                          };
  
                          if (root) {
                              importNode.root = root;
                              importNode.importedFilename = fullPath;
                              if (!inlineCSS && !importNode.skip) {
                                  new(tree.importVisitor)(importVisitor._importer, subFinish, env)
                                      .run(root);
                                  return;
                              }
                          }
  
                          subFinish();
                      });
                  }
              }
              visitArgs.visitDeeper = false;
              return importNode;
          },
          visitRule: function (ruleNode, visitArgs) {
              visitArgs.visitDeeper = false;
              return ruleNode;
          },
          visitDirective: function (directiveNode, visitArgs) {
              this.env.frames.unshift(directiveNode);
              return directiveNode;
          },
          visitDirectiveOut: function (directiveNode) {
              this.env.frames.shift();
          },
          visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
              this.env.frames.unshift(mixinDefinitionNode);
              return mixinDefinitionNode;
          },
          visitMixinDefinitionOut: function (mixinDefinitionNode) {
              this.env.frames.shift();
          },
          visitRuleset: function (rulesetNode, visitArgs) {
              this.env.frames.unshift(rulesetNode);
              return rulesetNode;
          },
          visitRulesetOut: function (rulesetNode) {
              this.env.frames.shift();
          },
          visitMedia: function (mediaNode, visitArgs) {
              this.env.frames.unshift(mediaNode.ruleset);
              return mediaNode;
          },
          visitMediaOut: function (mediaNode) {
              this.env.frames.shift();
          }
      };
  
  })(require('./tree'));
  (function (tree) {
      tree.joinSelectorVisitor = function() {
          this.contexts = [[]];
          this._visitor = new tree.visitor(this);
      };
  
      tree.joinSelectorVisitor.prototype = {
          run: function (root) {
              return this._visitor.visit(root);
          },
          visitRule: function (ruleNode, visitArgs) {
              visitArgs.visitDeeper = false;
          },
          visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
              visitArgs.visitDeeper = false;
          },
  
          visitRuleset: function (rulesetNode, visitArgs) {
              var context = this.contexts[this.contexts.length - 1],
                  paths = [], selectors;
  
              this.contexts.push(paths);
  
              if (! rulesetNode.root) {
                  selectors = rulesetNode.selectors;
                  if (selectors) {
                      selectors = selectors.filter(function(selector) { return selector.getIsOutput(); });
                      rulesetNode.selectors = selectors.length ? selectors : (selectors = null);
                      if (selectors) { rulesetNode.joinSelectors(paths, context, selectors); }
                  }
                  if (!selectors) { rulesetNode.rules = null; }
                  rulesetNode.paths = paths;
              }
          },
          visitRulesetOut: function (rulesetNode) {
              this.contexts.length = this.contexts.length - 1;
          },
          visitMedia: function (mediaNode, visitArgs) {
              var context = this.contexts[this.contexts.length - 1];
              mediaNode.rules[0].root = (context.length === 0 || context[0].multiMedia);
          }
      };
  
  })(require('./tree'));
  (function (tree) {
      tree.toCSSVisitor = function(env) {
          this._visitor = new tree.visitor(this);
          this._env = env;
      };
  
      tree.toCSSVisitor.prototype = {
          isReplacing: true,
          run: function (root) {
              return this._visitor.visit(root);
          },
  
          visitRule: function (ruleNode, visitArgs) {
              if (ruleNode.variable) {
                  return [];
              }
              return ruleNode;
          },
  
          visitMixinDefinition: function (mixinNode, visitArgs) {
              return [];
          },
  
          visitExtend: function (extendNode, visitArgs) {
              return [];
          },
  
          visitComment: function (commentNode, visitArgs) {
              if (commentNode.isSilent(this._env)) {
                  return [];
              }
              return commentNode;
          },
  
          visitMedia: function(mediaNode, visitArgs) {
              mediaNode.accept(this._visitor);
              visitArgs.visitDeeper = false;
  
              if (!mediaNode.rules.length) {
                  return [];
              }
              return mediaNode;
          },
  
          visitDirective: function(directiveNode, visitArgs) {
              if (directiveNode.currentFileInfo.reference && !directiveNode.isReferenced) {
                  return [];
              }
              if (directiveNode.name === "@charset") {
                  // Only output the debug info together with subsequent @charset definitions
                  // a comment (or @media statement) before the actual @charset directive would
                  // be considered illegal css as it has to be on the first line
                  if (this.charset) {
                      if (directiveNode.debugInfo) {
                          var comment = new tree.Comment("/* " + directiveNode.toCSS(this._env).replace(/\n/g, "")+" */\n");
                          comment.debugInfo = directiveNode.debugInfo;
                          return this._visitor.visit(comment);
                      }
                      return [];
                  }
                  this.charset = true;
              }
              return directiveNode;
          },
  
          checkPropertiesInRoot: function(rules) {
              var ruleNode;
              for(var i = 0; i < rules.length; i++) {
                  ruleNode = rules[i];
                  if (ruleNode instanceof tree.Rule && !ruleNode.variable) {
                      throw { message: "properties must be inside selector blocks, they cannot be in the root.",
                          index: ruleNode.index, filename: ruleNode.currentFileInfo ? ruleNode.currentFileInfo.filename : null};
                  }
              }
          },
  
          visitRuleset: function (rulesetNode, visitArgs) {
              var rule, rulesets = [];
              if (rulesetNode.firstRoot) {
                  this.checkPropertiesInRoot(rulesetNode.rules);
              }
              if (! rulesetNode.root) {
                  if (rulesetNode.paths) {
                      rulesetNode.paths = rulesetNode.paths
                          .filter(function(p) {
                              var i;
                              if (p[0].elements[0].combinator.value === ' ') {
                                  p[0].elements[0].combinator = new(tree.Combinator)('');
                              }
                              for(i = 0; i < p.length; i++) {
                                  if (p[i].getIsReferenced() && p[i].getIsOutput()) {
                                      return true;
                                  }
                              }
                              return false;
                          });
                  }
  
                  // Compile rules and rulesets
                  var nodeRules = rulesetNode.rules, nodeRuleCnt = nodeRules ? nodeRules.length : 0;
                  for (var i = 0; i < nodeRuleCnt; ) {
                      rule = nodeRules[i];
                      if (rule && rule.rules) {
                          // visit because we are moving them out from being a child
                          rulesets.push(this._visitor.visit(rule));
                          nodeRules.splice(i, 1);
                          nodeRuleCnt--;
                          continue;
                      }
                      i++;
                  }
                  // accept the visitor to remove rules and refactor itself
                  // then we can decide now whether we want it or not
                  if (nodeRuleCnt > 0) {
                      rulesetNode.accept(this._visitor);
                  } else {
                      rulesetNode.rules = null;
                  }
                  visitArgs.visitDeeper = false;
  
                  nodeRules = rulesetNode.rules;
                  if (nodeRules) {
                      this._mergeRules(nodeRules);
                      nodeRules = rulesetNode.rules;
                  }
                  if (nodeRules) {
                      this._removeDuplicateRules(nodeRules);
                      nodeRules = rulesetNode.rules;
                  }
  
                  // now decide whether we keep the ruleset
                  if (nodeRules && nodeRules.length > 0 && rulesetNode.paths.length > 0) {
                      rulesets.splice(0, 0, rulesetNode);
                  }
              } else {
                  rulesetNode.accept(this._visitor);
                  visitArgs.visitDeeper = false;
                  if (rulesetNode.firstRoot || (rulesetNode.rules && rulesetNode.rules.length > 0)) {
                      rulesets.splice(0, 0, rulesetNode);
                  }
              }
              if (rulesets.length === 1) {
                  return rulesets[0];
              }
              return rulesets;
          },
  
          _removeDuplicateRules: function(rules) {
              if (!rules) { return; }
  
              // remove duplicates
              var ruleCache = {},
                  ruleList, rule, i;
  
              for(i = rules.length - 1; i >= 0 ; i--) {
                  rule = rules[i];
                  if (rule instanceof tree.Rule) {
                      if (!ruleCache[rule.name]) {
                          ruleCache[rule.name] = rule;
                      } else {
                          ruleList = ruleCache[rule.name];
                          if (ruleList instanceof tree.Rule) {
                              ruleList = ruleCache[rule.name] = [ruleCache[rule.name].toCSS(this._env)];
                          }
                          var ruleCSS = rule.toCSS(this._env);
                          if (ruleList.indexOf(ruleCSS) !== -1) {
                              rules.splice(i, 1);
                          } else {
                              ruleList.push(ruleCSS);
                          }
                      }
                  }
              }
          },
  
          _mergeRules: function (rules) {
              if (!rules) { return; }
  
              var groups = {},
                  parts,
                  rule,
                  key;
  
              for (var i = 0; i < rules.length; i++) {
                  rule = rules[i];
  
                  if ((rule instanceof tree.Rule) && rule.merge) {
                      key = [rule.name,
                          rule.important ? "!" : ""].join(",");
  
                      if (!groups[key]) {
                          groups[key] = [];
                      } else {
                          rules.splice(i--, 1);
                      }
  
                      groups[key].push(rule);
                  }
              }
  
              Object.keys(groups).map(function (k) {
                  parts = groups[k];
  
                  if (parts.length > 1) {
                      rule = parts[0];
  
                      rule.value = new (tree.Value)(parts.map(function (p) {
                          return p.value;
                      }));
                  }
              });
          }
      };
  
  })(require('./tree'));
  (function (tree) {
      /*jshint loopfunc:true */
  
      tree.extendFinderVisitor = function() {
          this._visitor = new tree.visitor(this);
          this.contexts = [];
          this.allExtendsStack = [[]];
      };
  
      tree.extendFinderVisitor.prototype = {
          run: function (root) {
              root = this._visitor.visit(root);
              root.allExtends = this.allExtendsStack[0];
              return root;
          },
          visitRule: function (ruleNode, visitArgs) {
              visitArgs.visitDeeper = false;
          },
          visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
              visitArgs.visitDeeper = false;
          },
          visitRuleset: function (rulesetNode, visitArgs) {
              if (rulesetNode.root) {
                  return;
              }
  
              var i, j, extend, allSelectorsExtendList = [], extendList;
  
              // get &:extend(.a); rules which apply to all selectors in this ruleset
              var rules = rulesetNode.rules, ruleCnt = rules ? rules.length : 0;
              for(i = 0; i < ruleCnt; i++) {
                  if (rulesetNode.rules[i] instanceof tree.Extend) {
                      allSelectorsExtendList.push(rules[i]);
                      rulesetNode.extendOnEveryPath = true;
                  }
              }
  
              // now find every selector and apply the extends that apply to all extends
              // and the ones which apply to an individual extend
              var paths = rulesetNode.paths;
              for(i = 0; i < paths.length; i++) {
                  var selectorPath = paths[i],
                      selector = selectorPath[selectorPath.length - 1],
                      selExtendList = selector.extendList;
  
                  extendList = selExtendList ? selExtendList.slice(0).concat(allSelectorsExtendList)
                                             : allSelectorsExtendList;
  
                  if (extendList) {
                      extendList = extendList.map(function(allSelectorsExtend) {
                          return allSelectorsExtend.clone();
                      });
                  }
  
                  for(j = 0; j < extendList.length; j++) {
                      this.foundExtends = true;
                      extend = extendList[j];
                      extend.findSelfSelectors(selectorPath);
                      extend.ruleset = rulesetNode;
                      if (j === 0) { extend.firstExtendOnThisSelectorPath = true; }
                      this.allExtendsStack[this.allExtendsStack.length-1].push(extend);
                  }
              }
  
              this.contexts.push(rulesetNode.selectors);
          },
          visitRulesetOut: function (rulesetNode) {
              if (!rulesetNode.root) {
                  this.contexts.length = this.contexts.length - 1;
              }
          },
          visitMedia: function (mediaNode, visitArgs) {
              mediaNode.allExtends = [];
              this.allExtendsStack.push(mediaNode.allExtends);
          },
          visitMediaOut: function (mediaNode) {
              this.allExtendsStack.length = this.allExtendsStack.length - 1;
          },
          visitDirective: function (directiveNode, visitArgs) {
              directiveNode.allExtends = [];
              this.allExtendsStack.push(directiveNode.allExtends);
          },
          visitDirectiveOut: function (directiveNode) {
              this.allExtendsStack.length = this.allExtendsStack.length - 1;
          }
      };
  
      tree.processExtendsVisitor = function() {
          this._visitor = new tree.visitor(this);
      };
  
      tree.processExtendsVisitor.prototype = {
          run: function(root) {
              var extendFinder = new tree.extendFinderVisitor();
              extendFinder.run(root);
              if (!extendFinder.foundExtends) { return root; }
              root.allExtends = root.allExtends.concat(this.doExtendChaining(root.allExtends, root.allExtends));
              this.allExtendsStack = [root.allExtends];
              return this._visitor.visit(root);
          },
          doExtendChaining: function (extendsList, extendsListTarget, iterationCount) {
              //
              // chaining is different from normal extension.. if we extend an extend then we are not just copying, altering and pasting
              // the selector we would do normally, but we are also adding an extend with the same target selector
              // this means this new extend can then go and alter other extends
              //
              // this method deals with all the chaining work - without it, extend is flat and doesn't work on other extend selectors
              // this is also the most expensive.. and a match on one selector can cause an extension of a selector we had already processed if
              // we look at each selector at a time, as is done in visitRuleset
  
              var extendIndex, targetExtendIndex, matches, extendsToAdd = [], newSelector, extendVisitor = this, selectorPath, extend, targetExtend, newExtend;
  
              iterationCount = iterationCount || 0;
  
              //loop through comparing every extend with every target extend.
              // a target extend is the one on the ruleset we are looking at copy/edit/pasting in place
              // e.g.  .a:extend(.b) {}  and .b:extend(.c) {} then the first extend extends the second one
              // and the second is the target.
              // the seperation into two lists allows us to process a subset of chains with a bigger set, as is the
              // case when processing media queries
              for(extendIndex = 0; extendIndex < extendsList.length; extendIndex++){
                  for(targetExtendIndex = 0; targetExtendIndex < extendsListTarget.length; targetExtendIndex++){
  
                      extend = extendsList[extendIndex];
                      targetExtend = extendsListTarget[targetExtendIndex];
  
                      // look for circular references
                      if( extend.parent_ids.indexOf( targetExtend.object_id ) >= 0 ){ continue; }
  
                      // find a match in the target extends self selector (the bit before :extend)
                      selectorPath = [targetExtend.selfSelectors[0]];
                      matches = extendVisitor.findMatch(extend, selectorPath);
  
                      if (matches.length) {
  
                          // we found a match, so for each self selector..
                          extend.selfSelectors.forEach(function(selfSelector) {
  
                              // process the extend as usual
                              newSelector = extendVisitor.extendSelector(matches, selectorPath, selfSelector);
  
                              // but now we create a new extend from it
                              newExtend = new(tree.Extend)(targetExtend.selector, targetExtend.option, 0);
                              newExtend.selfSelectors = newSelector;
  
                              // add the extend onto the list of extends for that selector
                              newSelector[newSelector.length-1].extendList = [newExtend];
  
                              // record that we need to add it.
                              extendsToAdd.push(newExtend);
                              newExtend.ruleset = targetExtend.ruleset;
  
                              //remember its parents for circular references
                              newExtend.parent_ids = newExtend.parent_ids.concat(targetExtend.parent_ids, extend.parent_ids);
  
                              // only process the selector once.. if we have :extend(.a,.b) then multiple
                              // extends will look at the same selector path, so when extending
                              // we know that any others will be duplicates in terms of what is added to the css
                              if (targetExtend.firstExtendOnThisSelectorPath) {
                                  newExtend.firstExtendOnThisSelectorPath = true;
                                  targetExtend.ruleset.paths.push(newSelector);
                              }
                          });
                      }
                  }
              }
  
              if (extendsToAdd.length) {
                  // try to detect circular references to stop a stack overflow.
                  // may no longer be needed.
                  this.extendChainCount++;
                  if (iterationCount > 100) {
                      var selectorOne = "{unable to calculate}";
                      var selectorTwo = "{unable to calculate}";
                      try
                      {
                          selectorOne = extendsToAdd[0].selfSelectors[0].toCSS();
                          selectorTwo = extendsToAdd[0].selector.toCSS();
                      }
                      catch(e) {}
                      throw {message: "extend circular reference detected. One of the circular extends is currently:"+selectorOne+":extend(" + selectorTwo+")"};
                  }
  
                  // now process the new extends on the existing rules so that we can handle a extending b extending c ectending d extending e...
                  return extendsToAdd.concat(extendVisitor.doExtendChaining(extendsToAdd, extendsListTarget, iterationCount+1));
              } else {
                  return extendsToAdd;
              }
          },
          visitRule: function (ruleNode, visitArgs) {
              visitArgs.visitDeeper = false;
          },
          visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
              visitArgs.visitDeeper = false;
          },
          visitSelector: function (selectorNode, visitArgs) {
              visitArgs.visitDeeper = false;
          },
          visitRuleset: function (rulesetNode, visitArgs) {
              if (rulesetNode.root) {
                  return;
              }
              var matches, pathIndex, extendIndex, allExtends = this.allExtendsStack[this.allExtendsStack.length-1], selectorsToAdd = [], extendVisitor = this, selectorPath;
  
              // look at each selector path in the ruleset, find any extend matches and then copy, find and replace
  
              for(extendIndex = 0; extendIndex < allExtends.length; extendIndex++) {
                  for(pathIndex = 0; pathIndex < rulesetNode.paths.length; pathIndex++) {
                      selectorPath = rulesetNode.paths[pathIndex];
  
                      // extending extends happens initially, before the main pass
                      if (rulesetNode.extendOnEveryPath) { continue; }
                      var extendList = selectorPath[selectorPath.length-1].extendList;
                      if (extendList && extendList.length) { continue; }
  
                      matches = this.findMatch(allExtends[extendIndex], selectorPath);
  
                      if (matches.length) {
  
                          allExtends[extendIndex].selfSelectors.forEach(function(selfSelector) {
                              selectorsToAdd.push(extendVisitor.extendSelector(matches, selectorPath, selfSelector));
                          });
                      }
                  }
              }
              rulesetNode.paths = rulesetNode.paths.concat(selectorsToAdd);
          },
          findMatch: function (extend, haystackSelectorPath) {
              //
              // look through the haystack selector path to try and find the needle - extend.selector
              // returns an array of selector matches that can then be replaced
              //
              var haystackSelectorIndex, hackstackSelector, hackstackElementIndex, haystackElement,
                  targetCombinator, i,
                  extendVisitor = this,
                  needleElements = extend.selector.elements,
                  potentialMatches = [], potentialMatch, matches = [];
  
              // loop through the haystack elements
              for(haystackSelectorIndex = 0; haystackSelectorIndex < haystackSelectorPath.length; haystackSelectorIndex++) {
                  hackstackSelector = haystackSelectorPath[haystackSelectorIndex];
  
                  for(hackstackElementIndex = 0; hackstackElementIndex < hackstackSelector.elements.length; hackstackElementIndex++) {
  
                      haystackElement = hackstackSelector.elements[hackstackElementIndex];
  
                      // if we allow elements before our match we can add a potential match every time. otherwise only at the first element.
                      if (extend.allowBefore || (haystackSelectorIndex === 0 && hackstackElementIndex === 0)) {
                          potentialMatches.push({pathIndex: haystackSelectorIndex, index: hackstackElementIndex, matched: 0, initialCombinator: haystackElement.combinator});
                      }
  
                      for(i = 0; i < potentialMatches.length; i++) {
                          potentialMatch = potentialMatches[i];
  
                          // selectors add " " onto the first element. When we use & it joins the selectors together, but if we don't
                          // then each selector in haystackSelectorPath has a space before it added in the toCSS phase. so we need to work out
                          // what the resulting combinator will be
                          targetCombinator = haystackElement.combinator.value;
                          if (targetCombinator === '' && hackstackElementIndex === 0) {
                              targetCombinator = ' ';
                          }
  
                          // if we don't match, null our match to indicate failure
                          if (!extendVisitor.isElementValuesEqual(needleElements[potentialMatch.matched].value, haystackElement.value) ||
                              (potentialMatch.matched > 0 && needleElements[potentialMatch.matched].combinator.value !== targetCombinator)) {
                              potentialMatch = null;
                          } else {
                              potentialMatch.matched++;
                          }
  
                          // if we are still valid and have finished, test whether we have elements after and whether these are allowed
                          if (potentialMatch) {
                              potentialMatch.finished = potentialMatch.matched === needleElements.length;
                              if (potentialMatch.finished &&
                                  (!extend.allowAfter && (hackstackElementIndex+1 < hackstackSelector.elements.length || haystackSelectorIndex+1 < haystackSelectorPath.length))) {
                                  potentialMatch = null;
                              }
                          }
                          // if null we remove, if not, we are still valid, so either push as a valid match or continue
                          if (potentialMatch) {
                              if (potentialMatch.finished) {
                                  potentialMatch.length = needleElements.length;
                                  potentialMatch.endPathIndex = haystackSelectorIndex;
                                  potentialMatch.endPathElementIndex = hackstackElementIndex + 1; // index after end of match
                                  potentialMatches.length = 0; // we don't allow matches to overlap, so start matching again
                                  matches.push(potentialMatch);
                              }
                          } else {
                              potentialMatches.splice(i, 1);
                              i--;
                          }
                      }
                  }
              }
              return matches;
          },
          isElementValuesEqual: function(elementValue1, elementValue2) {
              if (typeof elementValue1 === "string" || typeof elementValue2 === "string") {
                  return elementValue1 === elementValue2;
              }
              if (elementValue1 instanceof tree.Attribute) {
                  if (elementValue1.op !== elementValue2.op || elementValue1.key !== elementValue2.key) {
                      return false;
                  }
                  if (!elementValue1.value || !elementValue2.value) {
                      if (elementValue1.value || elementValue2.value) {
                          return false;
                      }
                      return true;
                  }
                  elementValue1 = elementValue1.value.value || elementValue1.value;
                  elementValue2 = elementValue2.value.value || elementValue2.value;
                  return elementValue1 === elementValue2;
              }
              elementValue1 = elementValue1.value;
              elementValue2 = elementValue2.value;
              if (elementValue1 instanceof tree.Selector) {
                  if (!(elementValue2 instanceof tree.Selector) || elementValue1.elements.length !== elementValue2.elements.length) {
                      return false;
                  }
                  for(var i = 0; i <elementValue1.elements.length; i++) {
                      if (elementValue1.elements[i].combinator.value !== elementValue2.elements[i].combinator.value) {
                          if (i !== 0 || (elementValue1.elements[i].combinator.value || ' ') !== (elementValue2.elements[i].combinator.value || ' ')) {
                              return false;
                          }
                      }
                      if (!this.isElementValuesEqual(elementValue1.elements[i].value, elementValue2.elements[i].value)) {
                          return false;
                      }
                  }
                  return true;
              }
              return false;
          },
          extendSelector:function (matches, selectorPath, replacementSelector) {
  
              //for a set of matches, replace each match with the replacement selector
  
              var currentSelectorPathIndex = 0,
                  currentSelectorPathElementIndex = 0,
                  path = [],
                  matchIndex,
                  selector,
                  firstElement,
                  match,
                  newElements;
  
              for (matchIndex = 0; matchIndex < matches.length; matchIndex++) {
                  match = matches[matchIndex];
                  selector = selectorPath[match.pathIndex];
                  firstElement = new tree.Element(
                      match.initialCombinator,
                      replacementSelector.elements[0].value,
                      replacementSelector.elements[0].index,
                      replacementSelector.elements[0].currentFileInfo
                  );
  
                  if (match.pathIndex > currentSelectorPathIndex && currentSelectorPathElementIndex > 0) {
                      path[path.length - 1].elements = path[path.length - 1].elements.concat(selectorPath[currentSelectorPathIndex].elements.slice(currentSelectorPathElementIndex));
                      currentSelectorPathElementIndex = 0;
                      currentSelectorPathIndex++;
                  }
  
                  newElements = selector.elements
                      .slice(currentSelectorPathElementIndex, match.index)
                      .concat([firstElement])
                      .concat(replacementSelector.elements.slice(1));
  
                  if (currentSelectorPathIndex === match.pathIndex && matchIndex > 0) {
                      path[path.length - 1].elements =
                          path[path.length - 1].elements.concat(newElements);
                  } else {
                      path = path.concat(selectorPath.slice(currentSelectorPathIndex, match.pathIndex));
  
                      path.push(new tree.Selector(
                          newElements
                      ));
                  }
                  currentSelectorPathIndex = match.endPathIndex;
                  currentSelectorPathElementIndex = match.endPathElementIndex;
                  if (currentSelectorPathElementIndex >= selectorPath[currentSelectorPathIndex].elements.length) {
                      currentSelectorPathElementIndex = 0;
                      currentSelectorPathIndex++;
                  }
              }
  
              if (currentSelectorPathIndex < selectorPath.length && currentSelectorPathElementIndex > 0) {
                  path[path.length - 1].elements = path[path.length - 1].elements.concat(selectorPath[currentSelectorPathIndex].elements.slice(currentSelectorPathElementIndex));
                  currentSelectorPathIndex++;
              }
  
              path = path.concat(selectorPath.slice(currentSelectorPathIndex, selectorPath.length));
  
              return path;
          },
          visitRulesetOut: function (rulesetNode) {
          },
          visitMedia: function (mediaNode, visitArgs) {
              var newAllExtends = mediaNode.allExtends.concat(this.allExtendsStack[this.allExtendsStack.length-1]);
              newAllExtends = newAllExtends.concat(this.doExtendChaining(newAllExtends, mediaNode.allExtends));
              this.allExtendsStack.push(newAllExtends);
          },
          visitMediaOut: function (mediaNode) {
              this.allExtendsStack.length = this.allExtendsStack.length - 1;
          },
          visitDirective: function (directiveNode, visitArgs) {
              var newAllExtends = directiveNode.allExtends.concat(this.allExtendsStack[this.allExtendsStack.length-1]);
              newAllExtends = newAllExtends.concat(this.doExtendChaining(newAllExtends, directiveNode.allExtends));
              this.allExtendsStack.push(newAllExtends);
          },
          visitDirectiveOut: function (directiveNode) {
              this.allExtendsStack.length = this.allExtendsStack.length - 1;
          }
      };
  
  })(require('./tree'));
  
  (function (tree) {
  
      tree.sourceMapOutput = function (options) {
          this._css = [];
          this._rootNode = options.rootNode;
          this._writeSourceMap = options.writeSourceMap;
          this._contentsMap = options.contentsMap;
          this._contentsIgnoredCharsMap = options.contentsIgnoredCharsMap;
          this._sourceMapFilename = options.sourceMapFilename;
          this._outputFilename = options.outputFilename;
          this._sourceMapURL = options.sourceMapURL;
          if (options.sourceMapBasepath) {
              this._sourceMapBasepath = options.sourceMapBasepath.replace(/\\/g, '/');
          }
          this._sourceMapRootpath = options.sourceMapRootpath;
          this._outputSourceFiles = options.outputSourceFiles;
          this._sourceMapGeneratorConstructor = options.sourceMapGenerator || require("source-map").SourceMapGenerator;
  
          if (this._sourceMapRootpath && this._sourceMapRootpath.charAt(this._sourceMapRootpath.length-1) !== '/') {
              this._sourceMapRootpath += '/';
          }
  
          this._lineNumber = 0;
          this._column = 0;
      };
  
      tree.sourceMapOutput.prototype.normalizeFilename = function(filename) {
          filename = filename.replace(/\\/g, '/');
  
          if (this._sourceMapBasepath && filename.indexOf(this._sourceMapBasepath) === 0) {
              filename = filename.substring(this._sourceMapBasepath.length);
              if (filename.charAt(0) === '\\' || filename.charAt(0) === '/') {
                 filename = filename.substring(1);
              }
          }
          return (this._sourceMapRootpath || "") + filename;
      };
  
      tree.sourceMapOutput.prototype.add = function(chunk, fileInfo, index, mapLines) {
  
          //ignore adding empty strings
          if (!chunk) {
              return;
          }
  
          var lines,
              sourceLines,
              columns,
              sourceColumns,
              i;
  
          if (fileInfo) {
              var inputSource = this._contentsMap[fileInfo.filename];
              
              // remove vars/banner added to the top of the file
              if (this._contentsIgnoredCharsMap[fileInfo.filename]) {
                  // adjust the index
                  index -= this._contentsIgnoredCharsMap[fileInfo.filename];
                  if (index < 0) { index = 0; }
                  // adjust the source
                  inputSource = inputSource.slice(this._contentsIgnoredCharsMap[fileInfo.filename]);
              }
              inputSource = inputSource.substring(0, index);
              sourceLines = inputSource.split("\n");
              sourceColumns = sourceLines[sourceLines.length-1];
          }
  
          lines = chunk.split("\n");
          columns = lines[lines.length-1];
  
          if (fileInfo) {
              if (!mapLines) {
                  this._sourceMapGenerator.addMapping({ generated: { line: this._lineNumber + 1, column: this._column},
                      original: { line: sourceLines.length, column: sourceColumns.length},
                      source: this.normalizeFilename(fileInfo.filename)});
              } else {
                  for(i = 0; i < lines.length; i++) {
                      this._sourceMapGenerator.addMapping({ generated: { line: this._lineNumber + i + 1, column: i === 0 ? this._column : 0},
                          original: { line: sourceLines.length + i, column: i === 0 ? sourceColumns.length : 0},
                          source: this.normalizeFilename(fileInfo.filename)});
                  }
              }
          }
  
          if (lines.length === 1) {
              this._column += columns.length;
          } else {
              this._lineNumber += lines.length - 1;
              this._column = columns.length;
          }
  
          this._css.push(chunk);
      };
  
      tree.sourceMapOutput.prototype.isEmpty = function() {
          return this._css.length === 0;
      };
  
      tree.sourceMapOutput.prototype.toCSS = function(env) {
          this._sourceMapGenerator = new this._sourceMapGeneratorConstructor({ file: this._outputFilename, sourceRoot: null });
  
          if (this._outputSourceFiles) {
              for(var filename in this._contentsMap) {
                  if (this._contentsMap.hasOwnProperty(filename))
                  {
                      var source = this._contentsMap[filename];
                      if (this._contentsIgnoredCharsMap[filename]) {
                          source = source.slice(this._contentsIgnoredCharsMap[filename]);
                      }
                      this._sourceMapGenerator.setSourceContent(this.normalizeFilename(filename), source);
                  }
              }
          }
  
          this._rootNode.genCSS(env, this);
  
          if (this._css.length > 0) {
              var sourceMapURL,
                  sourceMapContent = JSON.stringify(this._sourceMapGenerator.toJSON());
  
              if (this._sourceMapURL) {
                  sourceMapURL = this._sourceMapURL;
              } else if (this._sourceMapFilename) {
                  sourceMapURL = this.normalizeFilename(this._sourceMapFilename);
              }
  
              if (this._writeSourceMap) {
                  this._writeSourceMap(sourceMapContent);
              } else {
                  sourceMapURL = "data:application/json," + encodeURIComponent(sourceMapContent);
              }
  
              if (sourceMapURL) {
                  this._css.push("/*# sourceMappingURL=" + sourceMapURL + " */");
              }
          }
  
          return this._css.join('');
      };
  
  })(require('./tree'));
  
  //
  // browser.js - client-side engine
  //
  /*global less, window, document, XMLHttpRequest, location */
  
  var isFileProtocol = /^(file|chrome(-extension)?|resource|qrc|app):/.test(location.protocol);
  
  less.env = less.env || (location.hostname == '127.0.0.1' ||
                          location.hostname == '0.0.0.0'   ||
                          location.hostname == 'localhost' ||
                          (location.port &&
                            location.port.length > 0)      ||
                          isFileProtocol                   ? 'development'
                                                           : 'production');
  
  var logLevel = {
      info: 2,
      errors: 1,
      none: 0
  };
  
  // The amount of logging in the javascript console.
  // 2 - Information and errors
  // 1 - Errors
  // 0 - None
  // Defaults to 2
  less.logLevel = typeof(less.logLevel) != 'undefined' ? less.logLevel : logLevel.info;
  
  // Load styles asynchronously (default: false)
  //
  // This is set to `false` by default, so that the body
  // doesn't start loading before the stylesheets are parsed.
  // Setting this to `true` can result in flickering.
  //
  less.async = less.async || false;
  less.fileAsync = less.fileAsync || false;
  
  // Interval between watch polls
  less.poll = less.poll || (isFileProtocol ? 1000 : 1500);
  
  //Setup user functions
  if (less.functions) {
      for(var func in less.functions) {
          if (less.functions.hasOwnProperty(func)) {
              less.tree.functions[func] = less.functions[func];
          }
     }
  }
  
  var dumpLineNumbers = /!dumpLineNumbers:(comments|mediaquery|all)/.exec(location.hash);
  if (dumpLineNumbers) {
      less.dumpLineNumbers = dumpLineNumbers[1];
  }
  
  var typePattern = /^text\/(x-)?less$/;
  var cache = null;
  var fileCache = {};
  
  function log(str, level) {
      if (less.env == 'development' && typeof(console) !== 'undefined' && less.logLevel >= level) {
          console.log('less: ' + str);
      }
  }
  
  function extractId(href) {
      return href.replace(/^[a-z-]+:\/+?[^\/]+/, '' )  // Remove protocol & domain
          .replace(/^\//,                 '' )  // Remove root /
          .replace(/\.[a-zA-Z]+$/,        '' )  // Remove simple extension
          .replace(/[^\.\w-]+/g,          '-')  // Replace illegal characters
          .replace(/\./g,                 ':'); // Replace dots with colons(for valid id)
  }
  
  function errorConsole(e, rootHref) {
      var template = '{line} {content}';
      var filename = e.filename || rootHref;
      var errors = [];
      var content = (e.type || "Syntax") + "Error: " + (e.message || 'There is an error in your .less file') +
          " in " + filename + " ";
  
      var errorline = function (e, i, classname) {
          if (e.extract[i] !== undefined) {
              errors.push(template.replace(/\{line\}/, (parseInt(e.line, 10) || 0) + (i - 1))
                  .replace(/\{class\}/, classname)
                  .replace(/\{content\}/, e.extract[i]));
          }
      };
  
      if (e.extract) {
          errorline(e, 0, '');
          errorline(e, 1, 'line');
          errorline(e, 2, '');
          content += 'on line ' + e.line + ', column ' + (e.column + 1) + ':\n' +
              errors.join('\n');
      } else if (e.stack) {
          content += e.stack;
      }
      log(content, logLevel.errors);
  }
  
  function createCSS(styles, sheet, lastModified) {
      // Strip the query-string
      var href = sheet.href || '';
  
      // If there is no title set, use the filename, minus the extension
      var id = 'less:' + (sheet.title || extractId(href));
  
      // If this has already been inserted into the DOM, we may need to replace it
      var oldCss = document.getElementById(id);
      var keepOldCss = false;
  
      // Create a new stylesheet node for insertion or (if necessary) replacement
      var css = document.createElement('style');
      css.setAttribute('type', 'text/css');
      if (sheet.media) {
          css.setAttribute('media', sheet.media);
      }
      css.id = id;
  
      if (css.styleSheet) { // IE
          try {
              css.styleSheet.cssText = styles;
          } catch (e) {
              throw new(Error)("Couldn't reassign styleSheet.cssText.");
          }
      } else {
          css.appendChild(document.createTextNode(styles));
  
          // If new contents match contents of oldCss, don't replace oldCss
          keepOldCss = (oldCss !== null && oldCss.childNodes.length > 0 && css.childNodes.length > 0 &&
              oldCss.firstChild.nodeValue === css.firstChild.nodeValue);
      }
  
      var head = document.getElementsByTagName('head')[0];
  
      // If there is no oldCss, just append; otherwise, only append if we need
      // to replace oldCss with an updated stylesheet
      if (oldCss === null || keepOldCss === false) {
          var nextEl = sheet && sheet.nextSibling || null;
          if (nextEl) {
              nextEl.parentNode.insertBefore(css, nextEl);
          } else {
              head.appendChild(css);
          }
      }
      if (oldCss && keepOldCss === false) {
          oldCss.parentNode.removeChild(oldCss);
      }
  
      // Don't update the local store if the file wasn't modified
      if (lastModified && cache) {
          log('saving ' + href + ' to cache.', logLevel.info);
          try {
              cache.setItem(href, styles);
              cache.setItem(href + ':timestamp', lastModified);
          } catch(e) {
              //TODO - could do with adding more robust error handling
              log('failed to save', logLevel.errors);
          }
      }
  }
  
  function errorHTML(e, rootHref) {
      var id = 'less-error-message:' + extractId(rootHref || "");
      var template = '<li><label>{line}</label><pre class="{class}">{content}</pre></li>';
      var elem = document.createElement('div'), timer, content, errors = [];
      var filename = e.filename || rootHref;
      var filenameNoPath = filename.match(/([^\/]+(\?.*)?)$/)[1];
  
      elem.id        = id;
      elem.className = "less-error-message";
  
      content = '<h3>'  + (e.type || "Syntax") + "Error: " + (e.message || 'There is an error in your .less file') +
          '</h3>' + '<p>in <a href="' + filename   + '">' + filenameNoPath + "</a> ";
  
      var errorline = function (e, i, classname) {
          if (e.extract[i] !== undefined) {
              errors.push(template.replace(/\{line\}/, (parseInt(e.line, 10) || 0) + (i - 1))
                  .replace(/\{class\}/, classname)
                  .replace(/\{content\}/, e.extract[i]));
          }
      };
  
      if (e.extract) {
          errorline(e, 0, '');
          errorline(e, 1, 'line');
          errorline(e, 2, '');
          content += 'on line ' + e.line + ', column ' + (e.column + 1) + ':</p>' +
              '<ul>' + errors.join('') + '</ul>';
      } else if (e.stack) {
          content += '<br/>' + e.stack.split('\n').slice(1).join('<br/>');
      }
      elem.innerHTML = content;
  
      // CSS for error messages
      createCSS([
          '.less-error-message ul, .less-error-message li {',
          'list-style-type: none;',
          'margin-right: 15px;',
          'padding: 4px 0;',
          'margin: 0;',
          '}',
          '.less-error-message label {',
          'font-size: 12px;',
          'margin-right: 15px;',
          'padding: 4px 0;',
          'color: #cc7777;',
          '}',
          '.less-error-message pre {',
          'color: #dd6666;',
          'padding: 4px 0;',
          'margin: 0;',
          'display: inline-block;',
          '}',
          '.less-error-message pre.line {',
          'color: #ff0000;',
          '}',
          '.less-error-message h3 {',
          'font-size: 20px;',
          'font-weight: bold;',
          'padding: 15px 0 5px 0;',
          'margin: 0;',
          '}',
          '.less-error-message a {',
          'color: #10a',
          '}',
          '.less-error-message .error {',
          'color: red;',
          'font-weight: bold;',
          'padding-bottom: 2px;',
          'border-bottom: 1px dashed red;',
          '}'
      ].join('\n'), { title: 'error-message' });
  
      elem.style.cssText = [
          "font-family: Arial, sans-serif",
          "border: 1px solid #e00",
          "background-color: #eee",
          "border-radius: 5px",
          "-webkit-border-radius: 5px",
          "-moz-border-radius: 5px",
          "color: #e00",
          "padding: 15px",
          "margin-bottom: 15px"
      ].join(';');
  
      if (less.env == 'development') {
          timer = setInterval(function () {
              if (document.body) {
                  if (document.getElementById(id)) {
                      document.body.replaceChild(elem, document.getElementById(id));
                  } else {
                      document.body.insertBefore(elem, document.body.firstChild);
                  }
                  clearInterval(timer);
              }
          }, 10);
      }
  }
  
  function error(e, rootHref) {
      if (!less.errorReporting || less.errorReporting === "html") {
          errorHTML(e, rootHref);
      } else if (less.errorReporting === "console") {
          errorConsole(e, rootHref);
      } else if (typeof less.errorReporting === 'function') {
          less.errorReporting("add", e, rootHref);
      }
  }
  
  function removeErrorHTML(path) {
      var node = document.getElementById('less-error-message:' + extractId(path));
      if (node) {
          node.parentNode.removeChild(node);
      }
  }
  
  function removeErrorConsole(path) {
      //no action
  }
  
  function removeError(path) {
      if (!less.errorReporting || less.errorReporting === "html") {
          removeErrorHTML(path);
      } else if (less.errorReporting === "console") {
          removeErrorConsole(path);
      } else if (typeof less.errorReporting === 'function') {
          less.errorReporting("remove", path);
      }
  }
  
  function loadStyles(modifyVars) {
      var styles = document.getElementsByTagName('style'),
          style;
      for (var i = 0; i < styles.length; i++) {
          style = styles[i];
          if (style.type.match(typePattern)) {
              var env = new less.tree.parseEnv(less),
                  lessText = style.innerHTML || '';
              env.filename = document.location.href.replace(/#.*$/, '');
  
              if (modifyVars || less.globalVars) {
                  env.useFileCache = true;
              }
  
              /*jshint loopfunc:true */
              // use closure to store current value of i
              var callback = (function(style) {
                  return function (e, cssAST) {
                      if (e) {
                          return error(e, "inline");
                      }
                      var css = cssAST.toCSS(less);
                      style.type = 'text/css';
                      if (style.styleSheet) {
                          style.styleSheet.cssText = css;
                      } else {
                          style.innerHTML = css;
                      }
                  };
              })(style);
              new(less.Parser)(env).parse(lessText, callback, {globalVars: less.globalVars, modifyVars: modifyVars});
          }
      }
  }
  
  function extractUrlParts(url, baseUrl) {
      // urlParts[1] = protocol&hostname || /
      // urlParts[2] = / if path relative to host base
      // urlParts[3] = directories
      // urlParts[4] = filename
      // urlParts[5] = parameters
  
      var urlPartsRegex = /^((?:[a-z-]+:)?\/+?(?:[^\/\?#]*\/)|([\/\\]))?((?:[^\/\\\?#]*[\/\\])*)([^\/\\\?#]*)([#\?].*)?$/i,
          urlParts = url.match(urlPartsRegex),
          returner = {}, directories = [], i, baseUrlParts;
  
      if (!urlParts) {
          throw new Error("Could not parse sheet href - '"+url+"'");
      }
  
      // Stylesheets in IE don't always return the full path
      if (!urlParts[1] || urlParts[2]) {
          baseUrlParts = baseUrl.match(urlPartsRegex);
          if (!baseUrlParts) {
              throw new Error("Could not parse page url - '"+baseUrl+"'");
          }
          urlParts[1] = urlParts[1] || baseUrlParts[1] || "";
          if (!urlParts[2]) {
              urlParts[3] = baseUrlParts[3] + urlParts[3];
          }
      }
  
      if (urlParts[3]) {
          directories = urlParts[3].replace(/\\/g, "/").split("/");
  
          // extract out . before .. so .. doesn't absorb a non-directory
          for(i = 0; i < directories.length; i++) {
              if (directories[i] === ".") {
                  directories.splice(i, 1);
                  i -= 1;
              }
          }
  
          for(i = 0; i < directories.length; i++) {
              if (directories[i] === ".." && i > 0) {
                  directories.splice(i-1, 2);
                  i -= 2;
              }
          }
      }
  
      returner.hostPart = urlParts[1];
      returner.directories = directories;
      returner.path = urlParts[1] + directories.join("/");
      returner.fileUrl = returner.path + (urlParts[4] || "");
      returner.url = returner.fileUrl + (urlParts[5] || "");
      return returner;
  }
  
  function pathDiff(url, baseUrl) {
      // diff between two paths to create a relative path
  
      var urlParts = extractUrlParts(url),
          baseUrlParts = extractUrlParts(baseUrl),
          i, max, urlDirectories, baseUrlDirectories, diff = "";
      if (urlParts.hostPart !== baseUrlParts.hostPart) {
          return "";
      }
      max = Math.max(baseUrlParts.directories.length, urlParts.directories.length);
      for(i = 0; i < max; i++) {
          if (baseUrlParts.directories[i] !== urlParts.directories[i]) { break; }
      }
      baseUrlDirectories = baseUrlParts.directories.slice(i);
      urlDirectories = urlParts.directories.slice(i);
      for(i = 0; i < baseUrlDirectories.length-1; i++) {
          diff += "../";
      }
      for(i = 0; i < urlDirectories.length-1; i++) {
          diff += urlDirectories[i] + "/";
      }
      return diff;
  }
  
  function getXMLHttpRequest() {
      if (window.XMLHttpRequest) {
          return new XMLHttpRequest();
      } else {
          try {
              /*global ActiveXObject */
              return new ActiveXObject("MSXML2.XMLHTTP.3.0");
          } catch (e) {
              log("browser doesn't support AJAX.", logLevel.errors);
              return null;
          }
      }
  }
  
  function doXHR(url, type, callback, errback) {
      var xhr = getXMLHttpRequest();
      var async = isFileProtocol ? less.fileAsync : less.async;
  
      if (typeof(xhr.overrideMimeType) === 'function') {
          xhr.overrideMimeType('text/css');
      }
      log("XHR: Getting '" + url + "'", logLevel.info);
      xhr.open('GET', url, async);
      xhr.setRequestHeader('Accept', type || 'text/x-less, text/css; q=0.9, */*; q=0.5');
      xhr.send(null);
  
      function handleResponse(xhr, callback, errback) {
          if (xhr.status >= 200 && xhr.status < 300) {
              callback(xhr.responseText,
                  xhr.getResponseHeader("Last-Modified"));
          } else if (typeof(errback) === 'function') {
              errback(xhr.status, url);
          }
      }
  
      if (isFileProtocol && !less.fileAsync) {
          if (xhr.status === 0 || (xhr.status >= 200 && xhr.status < 300)) {
              callback(xhr.responseText);
          } else {
              errback(xhr.status, url);
          }
      } else if (async) {
          xhr.onreadystatechange = function () {
              if (xhr.readyState == 4) {
                  handleResponse(xhr, callback, errback);
              }
          };
      } else {
          handleResponse(xhr, callback, errback);
      }
  }
  
  function loadFile(originalHref, currentFileInfo, callback, env, modifyVars) {
  
      if (currentFileInfo && currentFileInfo.currentDirectory && !/^([a-z-]+:)?\//.test(originalHref)) {
          originalHref = currentFileInfo.currentDirectory + originalHref;
      }
  
      // sheet may be set to the stylesheet for the initial load or a collection of properties including
      // some env variables for imports
      var hrefParts = extractUrlParts(originalHref, window.location.href);
      var href      = hrefParts.url;
      var newFileInfo = {
          currentDirectory: hrefParts.path,
          filename: href
      };
  
      if (currentFileInfo) {
          newFileInfo.entryPath = currentFileInfo.entryPath;
          newFileInfo.rootpath = currentFileInfo.rootpath;
          newFileInfo.rootFilename = currentFileInfo.rootFilename;
          newFileInfo.relativeUrls = currentFileInfo.relativeUrls;
      } else {
          newFileInfo.entryPath = hrefParts.path;
          newFileInfo.rootpath = less.rootpath || hrefParts.path;
          newFileInfo.rootFilename = href;
          newFileInfo.relativeUrls = env.relativeUrls;
      }
  
      if (newFileInfo.relativeUrls) {
          if (env.rootpath) {
              newFileInfo.rootpath = extractUrlParts(env.rootpath + pathDiff(hrefParts.path, newFileInfo.entryPath)).path;
          } else {
              newFileInfo.rootpath = hrefParts.path;
          }
      }
  
      if (env.useFileCache && fileCache[href]) {
          try {
              var lessText = fileCache[href];
              callback(null, lessText, href, newFileInfo, { lastModified: new Date() });
          } catch (e) {
              callback(e, null, href);
          }
          return;
      }
  
      doXHR(href, env.mime, function (data, lastModified) {
          // per file cache
          fileCache[href] = data;
  
          // Use remote copy (re-parse)
          try {
              callback(null, data, href, newFileInfo, { lastModified: lastModified });
          } catch (e) {
              callback(e, null, href);
          }
      }, function (status, url) {
          callback({ type: 'File', message: "'" + url + "' wasn't found (" + status + ")" }, null, href);
      });
  }
  
  function loadStyleSheet(sheet, callback, reload, remaining, modifyVars) {
  
      var env = new less.tree.parseEnv(less);
      env.mime = sheet.type;
  
      if (modifyVars || less.globalVars) {
          env.useFileCache = true;
      }
  
      loadFile(sheet.href, null, function(e, data, path, newFileInfo, webInfo) {
  
          if (webInfo) {
              webInfo.remaining = remaining;
  
              var css       = cache && cache.getItem(path),
                  timestamp = cache && cache.getItem(path + ':timestamp');
  
              if (!reload && timestamp && webInfo.lastModified &&
                  (new(Date)(webInfo.lastModified).valueOf() ===
                      new(Date)(timestamp).valueOf())) {
                  // Use local copy
                  createCSS(css, sheet);
                  webInfo.local = true;
                  callback(null, null, data, sheet, webInfo, path);
                  return;
              }
          }
  
          //TODO add tests around how this behaves when reloading
          removeError(path);
  
          if (data) {
              env.currentFileInfo = newFileInfo;
              new(less.Parser)(env).parse(data, function (e, root) {
                  if (e) { return callback(e, null, null, sheet); }
                  try {
                      callback(e, root, data, sheet, webInfo, path);
                  } catch (e) {
                      callback(e, null, null, sheet);
                  }
              }, {modifyVars: modifyVars, globalVars: less.globalVars});
          } else {
              callback(e, null, null, sheet, webInfo, path);
          }
      }, env, modifyVars);
  }
  
  function loadStyleSheets(callback, reload, modifyVars) {
      for (var i = 0; i < less.sheets.length; i++) {
          loadStyleSheet(less.sheets[i], callback, reload, less.sheets.length - (i + 1), modifyVars);
      }
  }
  
  function initRunningMode(){
      if (less.env === 'development') {
          less.optimization = 0;
          less.watchTimer = setInterval(function () {
              if (less.watchMode) {
                  loadStyleSheets(function (e, root, _, sheet, env) {
                      if (e) {
                          error(e, sheet.href);
                      } else if (root) {
                          createCSS(root.toCSS(less), sheet, env.lastModified);
                      }
                  });
              }
          }, less.poll);
      } else {
          less.optimization = 3;
      }
  }
  
  
  
  //
  // Watch mode
  //
  less.watch   = function () {
      if (!less.watchMode ){
          less.env = 'development';
           initRunningMode();
      }
      this.watchMode = true;
      return true;
  };
  
  less.unwatch = function () {clearInterval(less.watchTimer); this.watchMode = false; return false; };
  
  if (/!watch/.test(location.hash)) {
      less.watch();
  }
  
  if (less.env != 'development') {
      try {
          cache = (typeof(window.localStorage) === 'undefined') ? null : window.localStorage;
      } catch (_) {}
  }
  
  //
  // Get all <link> tags with the 'rel' attribute set to "stylesheet/less"
  //
  var links = document.getElementsByTagName('link');
  
  less.sheets = [];
  
  for (var i = 0; i < links.length; i++) {
      if (links[i].rel === 'stylesheet/less' || (links[i].rel.match(/stylesheet/) &&
         (links[i].type.match(typePattern)))) {
          less.sheets.push(links[i]);
      }
  }
  
  //
  // With this function, it's possible to alter variables and re-render
  // CSS without reloading less-files
  //
  less.modifyVars = function(record) {
      less.refresh(false, record);
  };
  
  less.refresh = function (reload, modifyVars) {
      var startTime, endTime;
      startTime = endTime = new Date();
  
      loadStyleSheets(function (e, root, _, sheet, env) {
          if (e) {
              return error(e, sheet.href);
          }
          if (env.local) {
              log("loading " + sheet.href + " from cache.", logLevel.info);
          } else {
              log("parsed " + sheet.href + " successfully.", logLevel.info);
              createCSS(root.toCSS(less), sheet, env.lastModified);
          }
          log("css for " + sheet.href + " generated in " + (new Date() - endTime) + 'ms', logLevel.info);
          if (env.remaining === 0) {
              log("css generated in " + (new Date() - startTime) + 'ms', logLevel.info);
          }
          endTime = new Date();
      }, reload, modifyVars);
  
      loadStyles(modifyVars);
  };
  
  less.refreshStyles = loadStyles;
  
  less.Parser.fileLoader = loadFile;
  
  less.refresh(less.env === 'development');
  
  // amd.js
  //
  // Define Less as an AMD module.
  if (typeof define === "function" && define.amd) {
      define(function () { return less; } );
  }
  
  })(window);