text: iD.ui.intro = function(context) {
  
      var step;
  
      function intro(selection) {
  
          context.enter(iD.modes.Browse(context));
  
          // Save current map state
          var history = context.history().toJSON(),
              hash = window.location.hash,
              background = context.background().baseLayerSource(),
              opacity = d3.select('.background-layer').style('opacity'),
              loadedTiles = context.connection().loadedTiles(),
              baseEntities = context.history().graph().base().entities,
              introGraph;
  
          // Load semi-real data used in intro
          context.connection().toggle(false).flush();
          context.history().save().reset();
          
          introGraph = JSON.parse(iD.introGraph);
          for (var key in introGraph) {
              introGraph[key] = iD.Entity(introGraph[key]);
          }
          context.history().merge(iD.Graph().load(introGraph).entities);
          context.background().bing();
  
          // Block saving
          var savebutton = d3.select('#bar button.save'),
              save = savebutton.on('click');
          savebutton.on('click', null);
  
          var beforeunload = window.onbeforeunload;
          window.onbeforeunload = null;
  
          d3.select('.background-layer').style('opacity', 1);
  
          var curtain = d3.curtain();
          selection.call(curtain);
  
          function reveal(box, text, options) {
              options = options || {};
              if (text) curtain.reveal(box, text, options.tooltipClass, options.duration);
              else curtain.reveal(box, '', '', options.duration);
          }
  
          var steps = ['navigation', 'point', 'area', 'line', 'startEditing'].map(function(step, i) {
              var s = iD.ui.intro[step](context, reveal)
                  .on('done', function() {
                      entered.filter(function(d) {
                          return d.title === s.title;
                      }).classed('finished', true);
                      enter(steps[i + 1]);
                  });
              return s;
          });
  
          steps[steps.length - 1].on('startEditing', function() {
              curtain.remove();
              navwrap.remove();
              d3.select('.background-layer').style('opacity', opacity);
              context.connection().toggle(true).flush().loadedTiles(loadedTiles);
              context.history().reset().merge(baseEntities);
              context.background().baseLayerSource(background);
              if (history) context.history().fromJSON(history);
              window.location.replace(hash);
              window.onbeforeunload = beforeunload;
              d3.select('#bar button.save').on('click', save);
          });
  
          var navwrap = selection.append('div').attr('class', 'intro-nav-wrap fillD');
  
          var buttonwrap = navwrap.append('div')
              .attr('class', 'joined')
              .selectAll('button.step');
  
          var entered = buttonwrap.data(steps)
              .enter().append('button')
                  .attr('class', 'step')
                  .on('click', enter);
  
          entered.append('div').attr('class','icon icon-pre-text apply');
          entered.append('label').text(function(d) { return t(d.title); });
          enter(steps[0]);
  
          function enter (newStep) {
  
              if (step) {
                  step.exit();
              }
  
              context.enter(iD.modes.Browse(context));
  
              step = newStep;
              step.enter();
  
              entered.classed('active', function(d) {
                  return d.title === step.title;
              });
          }
  
      }
      return intro;
  };
  
  iD.ui.intro.pointBox = function(point, context) {
      var rect = context.surfaceRect();
      point = context.projection(point);
      return {
          left: point[0] + rect.left - 30,
          top: point[1] + rect.top - 50,
          width: 60,
          height: 70
      };
  };
  
  iD.ui.intro.pad = function(box, padding, context) {
      if (box instanceof Array) {
          var rect = context.surfaceRect();
          box = context.projection(box);
          box = {
              left: box[0] + rect.left,
              top: box[1] + rect.top
          };
      }
      return {
          left: box.left - padding,
          top: box.top - padding,
          width: (box.width || 0) + 2 * padding,
          height: (box.width || 0) + 2 * padding
      };
  };
  