text: /*
  p5.play
  by Paolo Pedercini/molleindustria, 2015
  http://molleindustria.org/
  */
  
  (function(root, factory) {
  if (typeof define === 'function' && define.amd)
  define('p5.play', ['@code-dot-org/p5'], function(p5) { (factory(p5)); });
  else if (typeof exports === 'object')
  factory(require('@code-dot-org/p5'));
  else
  factory(root.p5);
  }(this, function(p5) {
  /**
   * p5.play is a library for p5.js to facilitate the creation of games and gamelike
   * projects.
   *
   * It provides a flexible Sprite class to manage visual objects in 2D space
   * and features such as animation support, basic collision detection
   * and resolution, mouse and keyboard interactions, and a virtual camera.
   *
   * p5.play is not a box2D-derived physics engine, it doesn't use events, and it's
   * designed to be understood and possibly modified by intermediate programmers.
   *
   * See the examples folder for more info on how to use this library.
   *
   * @module p5.play
   * @submodule p5.play
   * @for p5.play
   * @main
   */
  
  // =============================================================================
  //                         initialization
  // =============================================================================
  
  var DEFAULT_FRAME_RATE = 30;
  
  // This is the new way to initialize custom p5 properties for any p5 instance.
  // The goal is to migrate lazy P5 properties over to this method.
  // @see https://github.com/molleindustria/p5.play/issues/46
  p5.prototype.registerMethod('init', function p5PlayInit() {
    /**
     * The sketch camera automatically created at the beginning of a sketch.
     * A camera facilitates scrolling and zooming for scenes extending beyond
     * the canvas. A camera has a position, a zoom factor, and the mouse
     * coordinates relative to the view.
     *
     * In p5.js terms the camera wraps the whole drawing cycle in a
     * transformation matrix but it can be disabled anytime during the draw
     * cycle, for example to draw interface elements in an absolute position.
     *
     * @property camera
     * @type {camera}
     */
    this.camera = new Camera(this, 0, 0, 1);
    this.camera.init = false;
  
    this.angleMode(this.DEGREES);
    this.frameRate(DEFAULT_FRAME_RATE);
  
    this._defaultCanvasSize = {
      width: 400,
      height: 400
    };
  
    var startDate = new Date();
    this._startTime = startDate.getTime();
  
    // Temporary canvas for supporting tint operations from image elements;
    // see p5.prototype.imageElement()
    this._tempCanvas = document.createElement('canvas');
  });
  
  // This provides a way for us to lazily define properties that
  // are global to p5 instances.
  //
  // Note that this isn't just an optimization: p5 currently provides no
  // way for add-ons to be notified when new p5 instances are created, so
  // lazily creating these properties is the *only* mechanism available
  // to us. For more information, see:
  //
  // https://github.com/processing/p5.js/issues/1263
  function defineLazyP5Property(name, getter) {
    Object.defineProperty(p5.prototype, name, {
      configurable: true,
      enumerable: true,
      get: function() {
        var context = (this instanceof p5 && !this._isGlobal) ? this : window;
  
        if (typeof(context._p5PlayProperties) === 'undefined') {
          context._p5PlayProperties = {};
        }
        if (!(name in context._p5PlayProperties)) {
          context._p5PlayProperties[name] = getter.call(context);
        }
        return context._p5PlayProperties[name];
      }
    });
  }
  
  // This returns a factory function, suitable for passing to
  // defineLazyP5Property, that returns a subclass of the given
  // constructor that is always bound to a particular p5 instance.
  function boundConstructorFactory(constructor) {
    if (typeof(constructor) !== 'function')
      throw new Error('constructor must be a function');
  
    return function createBoundConstructor() {
      var pInst = this;
  
      function F() {
        var args = Array.prototype.slice.call(arguments);
  
        return constructor.apply(this, [pInst].concat(args));
      }
      F.prototype = constructor.prototype;
  
      return F;
    };
  }
  
  // This is a utility that makes it easy to define convenient aliases to
  // pre-bound p5 instance methods.
  //
  // For example:
  //
  //   var pInstBind = createPInstBinder(pInst);
  //
  //   var createVector = pInstBind('createVector');
  //   var loadImage = pInstBind('loadImage');
  //
  // The above will create functions createVector and loadImage, which can be
  // used similar to p5 global mode--however, they're bound to specific p5
  // instances, and can thus be used outside of global mode.
  function createPInstBinder(pInst) {
    return function pInstBind(methodName) {
      var method = pInst[methodName];
  
      if (typeof(method) !== 'function')
        throw new Error('"' + methodName + '" is not a p5 method');
      return method.bind(pInst);
    };
  }
  
  // These are utility p5 functions that don't depend on p5 instance state in
  // order to work properly, so we'll go ahead and make them easy to
  // access without needing to bind them to a p5 instance.
  var abs = p5.prototype.abs;
  var radians = p5.prototype.radians;
  var degrees = p5.prototype.degrees;
  
  // =============================================================================
  //                         p5 overrides
  // =============================================================================
  
  // Make the fill color default to gray (127, 127, 127) each time a new canvas is
  // created.
  if (!p5.prototype.originalCreateCanvas_) {
    p5.prototype.originalCreateCanvas_ = p5.prototype.createCanvas;
    p5.prototype.createCanvas = function() {
      var result = this.originalCreateCanvas_.apply(this, arguments);
      this.fill(this.color(127, 127, 127));
      return result;
    };
  }
  
  // Make width and height optional for ellipse() - default to 50
  // Save the original implementation to allow for optional parameters.
  if (!p5.prototype.originalEllipse_) {
    p5.prototype.originalEllipse_ = p5.prototype.ellipse;
    p5.prototype.ellipse = function(x, y, w, h) {
      w = (w) ? w : 50;
      h = (w && !h) ? w : h;
      this.originalEllipse_(x, y, w, h);
    };
  }
  
  // Make width and height optional for rect() - default to 50
  // Save the original implementation to allow for optional parameters.
  if (!p5.prototype.originalRect_) {
    p5.prototype.originalRect_ = p5.prototype.rect;
    p5.prototype.rect = function(x, y, w, h) {
      w = (w) ? w : 50;
      h = (w && !h) ? w : h;
      this.originalRect_(x, y, w, h);
    };
  }
  
  // Modify p5 to ignore out-of-bounds positions before setting touchIsDown
  p5.prototype._ontouchstart = function(e) {
    if (!this._curElement) {
      return;
    }
    var validTouch;
    for (var i = 0; i < e.touches.length; i++) {
      validTouch = getTouchInfo(this._curElement.elt, e, i);
      if (validTouch) {
        break;
      }
    }
    if (!validTouch) {
      // No in-bounds (valid) touches, return and ignore:
      return;
    }
    var context = this._isGlobal ? window : this;
    var executeDefault;
    this._updateNextTouchCoords(e);
    this._updateNextMouseCoords(e);
    this._setProperty('touchIsDown', true);
    if (typeof context.touchStarted === 'function') {
      executeDefault = context.touchStarted(e);
      if (executeDefault === false) {
        e.preventDefault();
      }
    } else if (typeof context.mousePressed === 'function') {
      executeDefault = context.mousePressed(e);
      if (executeDefault === false) {
        e.preventDefault();
      }
      //this._setMouseButton(e);
    }
  };
  
  // Modify p5 to handle CSS transforms (scale) and ignore out-of-bounds
  // positions before reporting touch coordinates
  //
  // NOTE: _updateNextTouchCoords() is nearly identical, but calls a modified
  // getTouchInfo() function below that scales the touch postion with the play
  // space and can return undefined
  p5.prototype._updateNextTouchCoords = function(e) {
    var x = this.touchX;
    var y = this.touchY;
    if (e.type === 'mousedown' || e.type === 'mousemove' ||
        e.type === 'mouseup' || !e.touches) {
      x = this.mouseX;
      y = this.mouseY;
    } else {
      if (this._curElement !== null) {
        var touchInfo = getTouchInfo(this._curElement.elt, e, 0);
        if (touchInfo) {
          x = touchInfo.x;
          y = touchInfo.y;
        }
  
        var touches = [];
        var touchIndex = 0;
        for (var i = 0; i < e.touches.length; i++) {
          // Only some touches are valid - only push valid touches into the
          // array for the `touches` property.
          touchInfo = getTouchInfo(this._curElement.elt, e, i);
          if (touchInfo) {
            touches[touchIndex] = touchInfo;
            touchIndex++;
          }
        }
        this._setProperty('touches', touches);
      }
    }
    this._setProperty('touchX', x);
    this._setProperty('touchY', y);
    if (!this._hasTouchInteracted) {
      // For first draw, make previous and next equal
      this._updateTouchCoords();
      this._setProperty('_hasTouchInteracted', true);
    }
  };
  
  // NOTE: returns undefined if the position is outside of the valid range
  function getTouchInfo(canvas, e, i) {
    i = i || 0;
    var rect = canvas.getBoundingClientRect();
    var touch = e.touches[i] || e.changedTouches[i];
    var xPos = touch.clientX - rect.left;
    var yPos = touch.clientY - rect.top;
    if (xPos >= 0 && xPos < rect.width && yPos >= 0 && yPos < rect.height) {
      return {
        x: Math.round(xPos * canvas.offsetWidth / rect.width),
        y: Math.round(yPos * canvas.offsetHeight / rect.height),
        id: touch.identifier
      };
    }
  }
  
  // Modify p5 to ignore out-of-bounds positions before setting mouseIsPressed
  // and isMousePressed
  p5.prototype._onmousedown = function(e) {
    if (!this._curElement) {
      return;
    }
    if (!getMousePos(this._curElement.elt, e)) {
      // Not in-bounds, return and ignore:
      return;
    }
    var context = this._isGlobal ? window : this;
    var executeDefault;
    this._setProperty('isMousePressed', true);
    this._setProperty('mouseIsPressed', true);
    this._setMouseButton(e);
    this._updateNextMouseCoords(e);
    this._updateNextTouchCoords(e);
    if (typeof context.mousePressed === 'function') {
      executeDefault = context.mousePressed(e);
      if (executeDefault === false) {
        e.preventDefault();
      }
    } else if (typeof context.touchStarted === 'function') {
      executeDefault = context.touchStarted(e);
      if (executeDefault === false) {
        e.preventDefault();
      }
    }
  };
  
  // Modify p5 to handle CSS transforms (scale) and ignore out-of-bounds
  // positions before reporting mouse coordinates
  //
  // NOTE: _updateNextMouseCoords() is nearly identical, but calls a modified
  // getMousePos() function below that scales the mouse position with the play
  // space and can return undefined.
  p5.prototype._updateNextMouseCoords = function(e) {
    var x = this.mouseX;
    var y = this.mouseY;
    if (e.type === 'touchstart' || e.type === 'touchmove' ||
        e.type === 'touchend' || e.touches) {
      x = this.touchX;
      y = this.touchY;
    } else if (this._curElement !== null) {
      var mousePos = getMousePos(this._curElement.elt, e);
      if (mousePos) {
        x = mousePos.x;
        y = mousePos.y;
      }
    }
    this._setProperty('mouseX', x);
    this._setProperty('mouseY', y);
    this._setProperty('winMouseX', e.pageX);
    this._setProperty('winMouseY', e.pageY);
    if (!this._hasMouseInteracted) {
      // For first draw, make previous and next equal
      this._updateMouseCoords();
      this._setProperty('_hasMouseInteracted', true);
    }
  };
  
  // NOTE: returns undefined if the position is outside of the valid range
  function getMousePos(canvas, evt) {
    var rect = canvas.getBoundingClientRect();
    var xPos = evt.clientX - rect.left;
    var yPos = evt.clientY - rect.top;
    if (xPos >= 0 && xPos < rect.width && yPos >= 0 && yPos < rect.height) {
      return {
        x: Math.round(xPos * canvas.offsetWidth / rect.width),
        y: Math.round(yPos * canvas.offsetHeight / rect.height)
      };
    }
  }
  
  // =============================================================================
  //                         p5 extensions
  // TODO: It'd be nice to get these accepted upstream in p5
  // =============================================================================
  
  /**
   * Projects a vector onto the line parallel to a second vector, giving a third
   * vector which is the orthogonal projection of that vector onto the line.
   * @see https://en.wikipedia.org/wiki/Vector_projection
   * @method project
   * @for p5.Vector
   * @static
   * @param {p5.Vector} a - vector being projected
   * @param {p5.Vector} b - vector defining the projection target line.
   * @return {p5.Vector} projection of a onto the line parallel to b.
   */
  p5.Vector.project = function(a, b) {
    return p5.Vector.mult(b, p5.Vector.dot(a, b) / p5.Vector.dot(b, b));
  };
  
  /**
   * Ask whether a vector is parallel to this one.
   * @method isParallel
   * @for p5.Vector
   * @param {p5.Vector} v2
   * @param {number} [tolerance] - margin of error for comparisons, comes into
   *        play when comparing rotated vectors.  For example, we want
   *        <1, 0> to be parallel to <0, 1>.rot(Math.PI/2) but float imprecision
   *        can get in the way of that.
   * @return {boolean}
   */
  p5.Vector.prototype.isParallel = function(v2, tolerance) {
    tolerance = typeof tolerance === 'number' ? tolerance : 1e-14;
    return (
        Math.abs(this.x) < tolerance && Math.abs(v2.x) < tolerance
      ) || (
        Math.abs(this.y ) < tolerance && Math.abs(v2.y) < tolerance
      ) || (
        Math.abs(this.x / v2.x - this.y / v2.y) < tolerance
      );
  };
  
  // =============================================================================
  //                         p5 additions
  // =============================================================================
  
  /**
   * Loads an image from a path and creates an Image from it.
   * <br><br>
   * The image may not be immediately available for rendering
   * If you want to ensure that the image is ready before doing
   * anything with it, place the loadImageElement() call in preload().
   * You may also supply a callback function to handle the image when it's ready.
   * <br><br>
   * The path to the image should be relative to the HTML file
   * that links in your sketch. Loading an from a URL or other
   * remote location may be blocked due to your browser's built-in
   * security.
   *
   * @method loadImageElement
   * @param  {String} path Path of the image to be loaded
   * @param  {Function(Image)} [successCallback] Function to be called once
   *                                the image is loaded. Will be passed the
   *                                Image.
   * @param  {Function(Event)}    [failureCallback] called with event error if
   *                                the image fails to load.
   * @return {Image}                the Image object
   */
  p5.prototype.loadImageElement = function(path, successCallback, failureCallback) {
    var img = new Image();
    var decrementPreload = p5._getDecrementPreload.apply(this, arguments);
  
    img.onload = function() {
      if (typeof successCallback === 'function') {
        successCallback(img);
      }
      if (decrementPreload && (successCallback !== decrementPreload)) {
        decrementPreload();
      }
    };
    img.onerror = function(e) {
      p5._friendlyFileLoadError(0, img.src);
      // don't get failure callback mixed up with decrementPreload
      if ((typeof failureCallback === 'function') &&
        (failureCallback !== decrementPreload)) {
        failureCallback(e);
      }
    };
  
    //set crossOrigin in case image is served which CORS headers
    //this will let us draw to canvas without tainting it.
    //see https://developer.mozilla.org/en-US/docs/HTML/CORS_Enabled_Image
    // When using data-uris the file will be loaded locally
    // so we don't need to worry about crossOrigin with base64 file types
    if(path.indexOf('data:image/') !== 0) {
      img.crossOrigin = 'Anonymous';
    }
  
    //start loading the image
    img.src = path;
  
    return img;
  };
  
  /**
   * Draw an image element to the main canvas of the p5js sketch
   *
   * @method imageElement
   * @param  {Image}    imgEl    the image to display
   * @param  {Number}   [sx=0]   The X coordinate of the top left corner of the
   *                             sub-rectangle of the source image to draw into
   *                             the destination canvas.
   * @param  {Number}   [sy=0]   The Y coordinate of the top left corner of the
   *                             sub-rectangle of the source image to draw into
   *                             the destination canvas.
   * @param {Number} [sWidth=imgEl.width] The width of the sub-rectangle of the
   *                                      source image to draw into the destination
   *                                      canvas.
   * @param {Number} [sHeight=imgEl.height] The height of the sub-rectangle of the
   *                                        source image to draw into the
   *                                        destination context.
   * @param  {Number}   [dx=0]    The X coordinate in the destination canvas at
   *                              which to place the top-left corner of the
   *                              source image.
   * @param  {Number}   [dy=0]    The Y coordinate in the destination canvas at
   *                              which to place the top-left corner of the
   *                              source image.
   * @param  {Number}   [dWidth]  The width to draw the image in the destination
   *                              canvas. This allows scaling of the drawn image.
   * @param  {Number}   [dHeight] The height to draw the image in the destination
   *                              canvas. This allows scaling of the drawn image.
   * @example
   * <div>
   * <code>
   * var imgEl;
   * function preload() {
   *   imgEl = loadImageElement("assets/laDefense.jpg");
   * }
   * function setup() {
   *   imageElement(imgEl, 0, 0);
   *   imageElement(imgEl, 0, 0, 100, 100);
   *   imageElement(imgEl, 0, 0, 100, 100, 0, 0, 100, 100);
   * }
   * </code>
   * </div>
   * <div>
   * <code>
   * function setup() {
   *   // here we use a callback to display the image after loading
   *   loadImageElement("assets/laDefense.jpg", function(imgEl) {
   *     imageElement(imgEl, 0, 0);
   *   });
   * }
   * </code>
   * </div>
   *
   * @alt
   * image of the underside of a white umbrella and grided ceiling above
   * image of the underside of a white umbrella and grided ceiling above
   *
   */
  p5.prototype.imageElement = function(imgEl, sx, sy, sWidth, sHeight, dx, dy, dWidth, dHeight) {
    /**
     * Validates clipping params. Per drawImage spec sWidth and sHight cannot be
     * negative or greater than image intrinsic width and height
     * @private
     * @param {Number} sVal
     * @param {Number} iVal
     * @returns {Number}
     * @private
     */
    function _sAssign(sVal, iVal) {
      if (sVal > 0 && sVal < iVal) {
        return sVal;
      }
      else {
        return iVal;
      }
    }
  
    function modeAdjust(a, b, c, d, mode) {
      if (mode === p5.prototype.CORNER) {
        return {x: a, y: b, w: c, h: d};
      } else if (mode === p5.prototype.CORNERS) {
        return {x: a, y: b, w: c-a, h: d-b};
      } else if (mode === p5.prototype.RADIUS) {
        return {x: a-c, y: b-d, w: 2*c, h: 2*d};
      } else if (mode === p5.prototype.CENTER) {
        return {x: a-c*0.5, y: b-d*0.5, w: c, h: d};
      }
    }
  
    if (arguments.length <= 5) {
      dx = sx || 0;
      dy = sy || 0;
      sx = 0;
      sy = 0;
      dWidth = sWidth || imgEl.width;
      dHeight = sHeight || imgEl.height;
      sWidth = imgEl.width;
      sHeight = imgEl.height;
    } else if (arguments.length === 9) {
      sx = sx || 0;
      sy = sy || 0;
      sWidth = _sAssign(sWidth, imgEl.width);
      sHeight = _sAssign(sHeight, imgEl.height);
  
      dx = dx || 0;
      dy = dy || 0;
      dWidth = dWidth || imgEl.width;
      dHeight = dHeight || imgEl.height;
    } else {
      throw 'Wrong number of arguments to imageElement()';
    }
  
    var vals = modeAdjust(dx, dy, dWidth, dHeight,
      this._renderer._imageMode);
  
    if (this._renderer._tint) {
      // Just-in-time create/draw into a temp canvas so tinting can
      // work within the renderer as it would for a p5.Image
      // Only resize canvas if it's too small
      var context = this._tempCanvas.getContext('2d');
      if (this._tempCanvas.width < vals.w || this._tempCanvas.height < vals.h) {
        this._tempCanvas.width = Math.max(this._tempCanvas.width, vals.w);
        this._tempCanvas.height = Math.max(this._tempCanvas.height, vals.h);
      } else {
        context.clearRect(0, 0, vals.w, vals.h);
      }
      context.drawImage(imgEl,
        sx, sy, sWidth, sHeight,
        0, 0, vals.w, vals.h);
      // Call the renderer's image() method with an object that contains the Image
      // as an 'elt' property and the temp canvas as well (when needed):
      this._renderer.image({canvas: this._tempCanvas},
        0, 0, vals.w, vals.h,
        vals.x, vals.y, vals.w, vals.h);
    } else {
      this._renderer.image({elt: imgEl},
        sx, sy, sWidth, sHeight,
        vals.x, vals.y, vals.w, vals.h);
    }
  };
  
  /**
  * A Group containing all the sprites in the sketch.
  *
  * @property allSprites
  * @for p5.play
  * @type {Group}
  */
  
  defineLazyP5Property('allSprites', function() {
    return new p5.prototype.Group();
  });
  
  p5.prototype._mouseButtonIsPressed = function(buttonCode) {
    return (this.mouseIsPressed && this.mouseButton === buttonCode) ||
      (this.touchIsDown && buttonCode === this.LEFT);
  };
  
  p5.prototype.mouseDidMove = function() {
    return this.pmouseX !== this.mouseX || this.pmouseY !== this.mouseY;
  };
  
  p5.prototype.mouseIsOver = function(sprite) {
    if (!sprite) {
      return false;
    }
  
    if (!sprite.collider) {
      sprite.setDefaultCollider();
    }
  
    var mousePosition;
    if (this.camera.active) {
      mousePosition = this.createVector(this.camera.mouseX, this.camera.mouseY);
    } else {
      mousePosition = this.createVector(this.mouseX, this.mouseY);
    }
  
    return sprite.collider.overlap(new window.p5.PointCollider(mousePosition));
  };
  
  p5.prototype.mousePressedOver = function(sprite) {
    return (this.mouseIsPressed || this.touchIsDown) && this.mouseIsOver(sprite);
  };
  
  var styleEmpty = 'rgba(0,0,0,0)';
  
  p5.Renderer2D.prototype.regularPolygon = function(x, y, sides, size, rotation) {
    var ctx = this.drawingContext;
    var doFill = this._doFill, doStroke = this._doStroke;
    if (doFill && !doStroke) {
      if (ctx.fillStyle === styleEmpty) {
        return this;
      }
    } else if (!doFill && doStroke) {
      if (ctx.strokeStyle === styleEmpty) {
        return this;
      }
    }
    if (sides < 3) {
      return;
    }
    ctx.beginPath();
    ctx.moveTo(x + size * Math.cos(rotation), y + size * Math.sin(rotation));
    for (var i = 1; i < sides; i++) {
      var angle = rotation + (i * 2 * Math.PI / sides);
      ctx.lineTo(x + size * Math.cos(angle), y + size * Math.sin(angle));
    }
    ctx.closePath();
    if (doFill) {
      ctx.fill();
    }
    if (doStroke) {
      ctx.stroke();
    }
  };
  
  p5.prototype.regularPolygon = function(x, y, sides, size, rotation) {
    if (!this._renderer._doStroke && !this._renderer._doFill) {
      return this;
    }
    var args = new Array(arguments.length);
    for (var i = 0; i < args.length; ++i) {
      args[i] = arguments[i];
    }
  
    if (typeof rotation === 'undefined') {
      rotation = -(Math.PI / 2);
      if (0 === sides % 2) {
        rotation += Math.PI / sides;
      }
    } else if (this._angleMode === this.DEGREES) {
      rotation = this.radians(rotation);
    }
  
    // NOTE: only implemented for non-3D
    if (!this._renderer.isP3D) {
      this._validateParameters(
        'regularPolygon',
        args,
        [
          ['Number', 'Number', 'Number', 'Number'],
          ['Number', 'Number', 'Number', 'Number', 'Number']
        ]
      );
      this._renderer.regularPolygon(
        args[0],
        args[1],
        args[2],
        args[3],
        rotation
      );
    }
    return this;
  };
  
  p5.Renderer2D.prototype.shape = function() {
    var ctx = this.drawingContext;
    var doFill = this._doFill, doStroke = this._doStroke;
    if (doFill && !doStroke) {
      if (ctx.fillStyle === styleEmpty) {
        return this;
      }
    } else if (!doFill && doStroke) {
      if (ctx.strokeStyle === styleEmpty) {
        return this;
      }
    }
    var numCoords = arguments.length / 2;
    if (numCoords < 1) {
      return;
    }
    ctx.beginPath();
    ctx.moveTo(arguments[0], arguments[1]);
    for (var i = 1; i < numCoords; i++) {
      ctx.lineTo(arguments[i * 2], arguments[i * 2 + 1]);
    }
    ctx.closePath();
    if (doFill) {
      ctx.fill();
    }
    if (doStroke) {
      ctx.stroke();
    }
  };
  
  p5.prototype.shape = function() {
    if (!this._renderer._doStroke && !this._renderer._doFill) {
      return this;
    }
    // NOTE: only implemented for non-3D
    if (!this._renderer.isP3D) {
      // TODO: call this._validateParameters, once it is working in p5.js and
      // we understand if it can be used for var args functions like this
      this._renderer.shape.apply(this._renderer, arguments);
    }
    return this;
  };
  
  p5.prototype.rgb = function(r, g, b, a) {
    // convert a from 0 to 255 to 0 to 1
    if (!a) {
      a = 1;
    }
    a = a * 255;
  
    return this.color(r, g, b, a);
  };
  
  p5.prototype.createGroup = function() {
    return new this.Group();
  };
  
  defineLazyP5Property('World', function() {
    var World = {
      pInst: this
    };
  
    function createReadOnlyP5PropertyAlias(name) {
      Object.defineProperty(World, name, {
        enumerable: true,
        get: function() {
          return this.pInst[name];
        }
      });
    }
  
    createReadOnlyP5PropertyAlias('width');
    createReadOnlyP5PropertyAlias('height');
    createReadOnlyP5PropertyAlias('mouseX');
    createReadOnlyP5PropertyAlias('mouseY');
    createReadOnlyP5PropertyAlias('allSprites');
    createReadOnlyP5PropertyAlias('frameCount');
  
    Object.defineProperty(World, 'frameRate', {
      enumerable: true,
      get: function() {
        return this.pInst.frameRate();
      },
      set: function(value) {
        this.pInst.frameRate(value);
      }
    });
  
    Object.defineProperty(World, 'seconds', {
      enumerable: true,
      get: function() {
        var currentDate = new Date();
        var currentTime = currentDate.getTime();
        return Math.round((currentTime - this.pInst._startTime) / 1000);
      }
    });
  
    return World;
  });
  
  p5.prototype.spriteUpdate = true;
  
  /**
     * A Sprite is the main building block of p5.play:
     * an element able to store images or animations with a set of
     * properties such as position and visibility.
     * A Sprite can have a collider that defines the active area to detect
     * collisions or overlappings with other sprites and mouse interactions.
     *
     * Sprites created using createSprite (the preferred way) are added to the
     * allSprites group and given a depth value that puts it in front of all
     * other sprites.
     *
     * @method createSprite
     * @param {Number} x Initial x coordinate
     * @param {Number} y Initial y coordinate
     * @param {Number} width Width of the placeholder rectangle and of the
     *                       collider until an image or new collider are set
     * @param {Number} height Height of the placeholder rectangle and of the
     *                       collider until an image or new collider are set
     * @return {Object} The new sprite instance
     */
  
  p5.prototype.createSprite = function(x, y, width, height) {
    var s = new Sprite(this, x, y, width, height);
    s.depth = this.allSprites.maxDepth()+1;
    this.allSprites.add(s);
    return s;
  };
  
  
  /**
     * Removes a Sprite from the sketch.
     * The removed Sprite won't be drawn or updated anymore.
     * Equivalent to Sprite.remove()
     *
     * @method removeSprite
     * @param {Object} sprite Sprite to be removed
  */
  p5.prototype.removeSprite = function(sprite) {
    sprite.remove();
  };
  
  /**
  * Updates all the sprites in the sketch (position, animation...)
  * it's called automatically at every draw().
  * It can be paused by passing a parameter true or false;
  * Note: it does not render the sprites.
  *
  * @method updateSprites
  * @param {Boolean} updating false to pause the update, true to resume
  */
  p5.prototype.updateSprites = function(upd) {
  
    if(upd === false)
      this.spriteUpdate = false;
    if(upd === true)
      this.spriteUpdate = true;
  
    if(this.spriteUpdate)
    for(var i = 0; i<this.allSprites.size(); i++)
    {
      this.allSprites.get(i).update();
    }
  };
  
  /**
  * Returns all the sprites in the sketch as an array
  *
  * @method getSprites
  * @return {Array} Array of Sprites
  */
  p5.prototype.getSprites = function() {
  
    //draw everything
    if(arguments.length===0)
    {
      return this.allSprites.toArray();
    }
    else
    {
      var arr = [];
      //for every tag
      for(var j=0; j<arguments.length; j++)
      {
        for(var i = 0; i<this.allSprites.size(); i++)
        {
          if(this.allSprites.get(i).isTagged(arguments[j]))
            arr.push(this.allSprites.get(i));
        }
      }
  
      return arr;
    }
  
  };
  
  /**
  * Displays a Group of sprites.
  * If no parameter is specified, draws all sprites in the
  * sketch.
  * The drawing order is determined by the Sprite property "depth"
  *
  * @method drawSprites
  * @param {Group} [group] Group of Sprites to be displayed
  */
  p5.prototype.drawSprites = function(group) {
    // If no group is provided, draw the allSprites group.
    group = group || this.allSprites;
  
    if (typeof group.draw !== 'function')
    {
      throw('Error: with drawSprites you can only draw all sprites or a group');
    }
  
    group.draw();
  };
  
  /**
  * Displays a Sprite.
  * To be typically used in the main draw function.
  *
  * @method drawSprite
  * @param {Sprite} sprite Sprite to be displayed
  */
  p5.prototype.drawSprite = function(sprite) {
    if(sprite)
    sprite.display();
  };
  
  /**
  * Loads an animation.
  * To be typically used in the preload() function of the sketch.
  *
  * @method loadAnimation
  * @param {Sprite} sprite Sprite to be displayed
  */
  p5.prototype.loadAnimation = function() {
    return construct(this.Animation, arguments);
  };
  
  /**
   * Loads a Sprite Sheet.
   * To be typically used in the preload() function of the sketch.
   *
   * @method loadSpriteSheet
   */
  p5.prototype.loadSpriteSheet = function() {
    return construct(this.SpriteSheet, arguments);
  };
  
  /**
  * Displays an animation.
  *
  * @method animation
  * @param {Animation} anim Animation to be displayed
  * @param {Number} x X coordinate
  * @param {Number} y Y coordinate
  *
  */
  p5.prototype.animation = function(anim, x, y) {
    anim.draw(x, y);
  };
  
  //variable to detect instant presses
  defineLazyP5Property('_p5play', function() {
    return {
      keyStates: {},
      mouseStates: {}
    };
  });
  
  var KEY_IS_UP = 0;
  var KEY_WENT_DOWN = 1;
  var KEY_IS_DOWN = 2;
  var KEY_WENT_UP = 3;
  
  /**
  * Detects if a key was pressed during the last cycle.
  * It can be used to trigger events once, when a key is pressed or released.
  * Example: Super Mario jumping.
  *
  * @method keyWentDown
  * @param {Number|String} key Key code or character
  * @return {Boolean} True if the key was pressed
  */
  p5.prototype.keyWentDown = function(key) {
    return this._isKeyInState(key, KEY_WENT_DOWN);
  };
  
  
  /**
  * Detects if a key was released during the last cycle.
  * It can be used to trigger events once, when a key is pressed or released.
  * Example: Spaceship shooting.
  *
  * @method keyWentUp
  * @param {Number|String} key Key code or character
  * @return {Boolean} True if the key was released
  */
  p5.prototype.keyWentUp = function(key) {
    return this._isKeyInState(key, KEY_WENT_UP);
  };
  
  /**
  * Detects if a key is currently pressed
  * Like p5 keyIsDown but accepts strings and codes
  *
  * @method keyDown
  * @param {Number|String} key Key code or character
  * @return {Boolean} True if the key is down
  */
  p5.prototype.keyDown = function(key) {
    return this._isKeyInState(key, KEY_IS_DOWN);
  };
  
  /**
   * Detects if a key is in the given state during the last cycle.
   * Helper method encapsulating common key state logic; it may be preferable
   * to call keyDown or other methods directly.
   *
   * @private
   * @method _isKeyInState
   * @param {Number|String} key Key code or character
   * @param {Number} state Key state to check against
   * @return {Boolean} True if the key is in the given state
   */
  p5.prototype._isKeyInState = function(key, state) {
    var keyCode;
    var keyStates = this._p5play.keyStates;
  
    if(typeof key === 'string')
    {
      keyCode = this._keyCodeFromAlias(key);
    }
    else
    {
      keyCode = key;
    }
  
    //if undefined start checking it
    if(keyStates[keyCode]===undefined)
    {
      if(this.keyIsDown(keyCode))
        keyStates[keyCode] = KEY_IS_DOWN;
      else
        keyStates[keyCode] = KEY_IS_UP;
    }
  
    return (keyStates[keyCode] === state);
  };
  
  /**
  * Detects if a mouse button is currently down
  * Combines mouseIsPressed and mouseButton of p5
  *
  * @method mouseDown
  * @param {Number} [buttonCode] Mouse button constant LEFT, RIGHT or CENTER
  * @return {Boolean} True if the button is down
  */
  p5.prototype.mouseDown = function(buttonCode) {
    return this._isMouseButtonInState(buttonCode, KEY_IS_DOWN);
  };
  
  /**
  * Detects if a mouse button is currently up
  * Combines mouseIsPressed and mouseButton of p5
  *
  * @method mouseUp
  * @param {Number} [buttonCode] Mouse button constant LEFT, RIGHT or CENTER
  * @return {Boolean} True if the button is up
  */
  p5.prototype.mouseUp = function(buttonCode) {
    return this._isMouseButtonInState(buttonCode, KEY_IS_UP);
  };
  
  /**
   * Detects if a mouse button was released during the last cycle.
   * It can be used to trigger events once, to be checked in the draw cycle
   *
   * @method mouseWentUp
   * @param {Number} [buttonCode] Mouse button constant LEFT, RIGHT or CENTER
   * @return {Boolean} True if the button was just released
   */
  p5.prototype.mouseWentUp = function(buttonCode) {
    return this._isMouseButtonInState(buttonCode, KEY_WENT_UP);
  };
  
  
  /**
   * Detects if a mouse button was pressed during the last cycle.
   * It can be used to trigger events once, to be checked in the draw cycle
   *
   * @method mouseWentDown
   * @param {Number} [buttonCode] Mouse button constant LEFT, RIGHT or CENTER
   * @return {Boolean} True if the button was just pressed
   */
  p5.prototype.mouseWentDown = function(buttonCode) {
    return this._isMouseButtonInState(buttonCode, KEY_WENT_DOWN);
  };
  
  /**
   * Returns a constant for a mouse state given a string or a mouse button constant.
   *
   * @private
   * @method _clickKeyFromString
   * @param {Number|String} [buttonCode] Mouse button constant LEFT, RIGHT or CENTER
   *   or string 'leftButton', 'rightButton', or 'centerButton'
   * @return {Number} Mouse button constant LEFT, RIGHT or CENTER or value of buttonCode
   */
  p5.prototype._clickKeyFromString = function(buttonCode) {
    if (this.CLICK_KEY[buttonCode]) {
      return this.CLICK_KEY[buttonCode];
    } else {
      return buttonCode;
    }
  };
  
  // Map of strings to constants for mouse states.
  p5.prototype.CLICK_KEY = {
    'leftButton': p5.prototype.LEFT,
    'rightButton': p5.prototype.RIGHT,
    'centerButton': p5.prototype.CENTER
  };
  
  /**
   * Detects if a mouse button is in the given state during the last cycle.
   * Helper method encapsulating common mouse button state logic; it may be
   * preferable to call mouseWentUp, etc, directly.
   *
   * @private
   * @method _isMouseButtonInState
   * @param {Number|String} [buttonCode] Mouse button constant LEFT, RIGHT or CENTER
   *   or string 'leftButton', 'rightButton', or 'centerButton'
   * @param {Number} state
   * @return {boolean} True if the button was in the given state
   */
  p5.prototype._isMouseButtonInState = function(buttonCode, state) {
    var mouseStates = this._p5play.mouseStates;
  
    buttonCode = this._clickKeyFromString(buttonCode);
  
    if(buttonCode === undefined)
      buttonCode = this.LEFT;
  
    //undefined = not tracked yet, start tracking
    if(mouseStates[buttonCode]===undefined)
    {
    if (this._mouseButtonIsPressed(buttonCode))
      mouseStates[buttonCode] = KEY_IS_DOWN;
    else
      mouseStates[buttonCode] = KEY_IS_UP;
    }
  
    return (mouseStates[buttonCode] === state);
  };
  
  
  /**
   * An object storing all useful keys for easy access
   * Key.tab = 9
   *
   * @private
   * @property KEY
   * @type {Object}
   */
  p5.prototype.KEY = {
      'BACKSPACE': 8,
      'TAB': 9,
      'ENTER': 13,
      'SHIFT': 16,
      'CTRL': 17,
      'ALT': 18,
      'PAUSE': 19,
      'CAPS_LOCK': 20,
      'ESC': 27,
      'SPACE': 32,
      ' ': 32,
      'PAGE_UP': 33,
      'PAGE_DOWN': 34,
      'END': 35,
      'HOME': 36,
      'LEFT_ARROW': 37,
      'LEFT': 37,
      'UP_ARROW': 38,
      'UP': 38,
      'RIGHT_ARROW': 39,
      'RIGHT': 39,
      'DOWN_ARROW': 40,
      'DOWN': 40,
      'INSERT': 45,
      'DELETE': 46,
      '0': 48,
      '1': 49,
      '2': 50,
      '3': 51,
      '4': 52,
      '5': 53,
      '6': 54,
      '7': 55,
      '8': 56,
      '9': 57,
      'A': 65,
      'B': 66,
      'C': 67,
      'D': 68,
      'E': 69,
      'F': 70,
      'G': 71,
      'H': 72,
      'I': 73,
      'J': 74,
      'K': 75,
      'L': 76,
      'M': 77,
      'N': 78,
      'O': 79,
      'P': 80,
      'Q': 81,
      'R': 82,
      'S': 83,
      'T': 84,
      'U': 85,
      'V': 86,
      'W': 87,
      'X': 88,
      'Y': 89,
      'Z': 90,
      '0NUMPAD': 96,
      '1NUMPAD': 97,
      '2NUMPAD': 98,
      '3NUMPAD': 99,
      '4NUMPAD': 100,
      '5NUMPAD': 101,
      '6NUMPAD': 102,
      '7NUMPAD': 103,
      '8NUMPAD': 104,
      '9NUMPAD': 105,
      'MULTIPLY': 106,
      'PLUS': 107,
      'MINUS': 109,
      'DOT': 110,
      'SLASH1': 111,
      'F1': 112,
      'F2': 113,
      'F3': 114,
      'F4': 115,
      'F5': 116,
      'F6': 117,
      'F7': 118,
      'F8': 119,
      'F9': 120,
      'F10': 121,
      'F11': 122,
      'F12': 123,
      'EQUAL': 187,
      'COMMA': 188,
      'SLASH': 191,
      'BACKSLASH': 220
  };
  
  /**
   * An object storing deprecated key aliases, which we still support but
   * should be mapped to valid aliases and generate warnings.
   *
   * @private
   * @property KEY_DEPRECATIONS
   * @type {Object}
   */
  p5.prototype.KEY_DEPRECATIONS = {
    'MINUT': 'MINUS',
    'COMA': 'COMMA'
  };
  
  /**
   * Given a string key alias (as defined in the KEY property above), look up
   * and return the numeric JavaScript key code for that key.  If a deprecated
   * alias is passed (as defined in the KEY_DEPRECATIONS property) it will be
   * mapped to a valid key code, but will also generate a warning about use
   * of the deprecated alias.
   *
   * @private
   * @method _keyCodeFromAlias
   * @param {!string} alias - a case-insensitive key alias
   * @return {number|undefined} a numeric JavaScript key code, or undefined
   *          if no key code matching the given alias is found.
   */
  p5.prototype._keyCodeFromAlias = function(alias) {
    alias = alias.toUpperCase();
    if (this.KEY_DEPRECATIONS[alias]) {
      this._warn('Key literal "' + alias + '" is deprecated and may be removed ' +
        'in a future version of p5.play. ' +
        'Please use "' + this.KEY_DEPRECATIONS[alias] + '" instead.');
      alias = this.KEY_DEPRECATIONS[alias];
    }
    return this.KEY[alias];
  };
  
  //pre draw: detect keyStates
  p5.prototype.readPresses = function() {
    var keyStates = this._p5play.keyStates;
    var mouseStates = this._p5play.mouseStates;
  
    for (var key in keyStates) {
      if(this.keyIsDown(key)) //if is down
      {
        if(keyStates[key] === KEY_IS_UP)//and was up
          keyStates[key] = KEY_WENT_DOWN;
        else
          keyStates[key] = KEY_IS_DOWN; //now is simply down
      }
      else //if it's up
      {
        if(keyStates[key] === KEY_IS_DOWN)//and was up
          keyStates[key] = KEY_WENT_UP;
        else
          keyStates[key] = KEY_IS_UP; //now is simply down
      }
    }
  
    //mouse
    for (var btn in mouseStates) {
  
      if(this._mouseButtonIsPressed(btn)) //if is down
      {
        if(mouseStates[btn] === KEY_IS_UP)//and was up
          mouseStates[btn] = KEY_WENT_DOWN;
        else
          mouseStates[btn] = KEY_IS_DOWN; //now is simply down
      }
      else //if it's up
      {
        if(mouseStates[btn] === KEY_IS_DOWN)//and was up
          mouseStates[btn] = KEY_WENT_UP;
        else
          mouseStates[btn] = KEY_IS_UP; //now is simply down
      }
    }
  
  };
  
  /**
  * Turns the quadTree on or off.
  * A quadtree is a data structure used to optimize collision detection.
  * It can improve performance when there is a large number of Sprites to be
  * checked continuously for overlapping.
  *
  * p5.play will create and update a quadtree automatically, however it is
  * inactive by default.
  *
  * @method useQuadTree
  * @param {Boolean} use Pass true to enable, false to disable
  */
  p5.prototype.useQuadTree = function(use) {
  
    if(this.quadTree !== undefined)
    {
      if(use === undefined)
        return this.quadTree.active;
      else if(use)
        this.quadTree.active = true;
      else
        this.quadTree.active = false;
    }
    else
      return false;
  };
  
  //the actual quadTree
  defineLazyP5Property('quadTree', function() {
    var quadTree = new Quadtree({
      x: 0,
      y: 0,
      width: 0,
      height: 0
    }, 4);
    quadTree.active = false;
    return quadTree;
  });
  
  /*
  //framerate independent delta, doesn't really work
  p5.prototype.deltaTime = 1;
  
  var now = Date.now();
  var then = Date.now();
  var INTERVAL_60 = 0.0166666; //60 fps
  
  function updateDelta() {
  then = now;
  now = Date.now();
  deltaTime = ((now - then) / 1000)/INTERVAL_60; // seconds since last frame
  }
  */
  
  /**
     * A Sprite is the main building block of p5.play:
     * an element able to store images or animations with a set of
     * properties such as position and visibility.
     * A Sprite can have a collider that defines the active area to detect
     * collisions or overlappings with other sprites and mouse interactions.
     *
     * To create a Sprite, use
     * {{#crossLink "p5.play/createSprite:method"}}{{/crossLink}}.
     *
     * @class Sprite
     */
  
  // For details on why these docs aren't in a YUIDoc comment block, see:
  //
  // https://github.com/molleindustria/p5.play/pull/67
  //
  // @param {Number} x Initial x coordinate
  // @param {Number} y Initial y coordinate
  // @param {Number} width Width of the placeholder rectangle and of the
  //                       collider until an image or new collider are set
  // @param {Number} height Height of the placeholder rectangle and of the
  //                        collider until an image or new collider are set
  function Sprite(pInst, _x, _y, _w, _h) {
    var pInstBind = createPInstBinder(pInst);
  
    var createVector = pInstBind('createVector');
    var color = pInstBind('color');
    var print = pInstBind('print');
    var push = pInstBind('push');
    var pop = pInstBind('pop');
    var colorMode = pInstBind('colorMode');
    var tint = pInstBind('tint');
    var lerpColor = pInstBind('lerpColor');
    var noStroke = pInstBind('noStroke');
    var rectMode = pInstBind('rectMode');
    var ellipseMode = pInstBind('ellipseMode');
    var imageMode = pInstBind('imageMode');
    var translate = pInstBind('translate');
    var scale = pInstBind('scale');
    var rotate = pInstBind('rotate');
    var stroke = pInstBind('stroke');
    var strokeWeight = pInstBind('strokeWeight');
    var line = pInstBind('line');
    var noFill = pInstBind('noFill');
    var fill = pInstBind('fill');
    var textAlign = pInstBind('textAlign');
    var textSize = pInstBind('textSize');
    var text = pInstBind('text');
    var rect = pInstBind('rect');
    var cos = pInstBind('cos');
    var sin = pInstBind('sin');
    var atan2 = pInstBind('atan2');
  
    var quadTree = pInst.quadTree;
    var camera = pInst.camera;
  
  
    // These are p5 constants that we'd like easy access to.
    var RGB = p5.prototype.RGB;
    var CENTER = p5.prototype.CENTER;
    var LEFT = p5.prototype.LEFT;
    var BOTTOM = p5.prototype.BOTTOM;
  
    /**
    * The sprite's position of the sprite as a vector (x,y).
    * @property position
    * @type {p5.Vector}
    */
    this.position = createVector(_x, _y);
  
    /**
    * The sprite's position at the beginning of the last update as a vector (x,y).
    * @property previousPosition
    * @type {p5.Vector}
    */
    this.previousPosition = createVector(_x, _y);
  
    /*
    The sprite's position at the end of the last update as a vector (x,y).
    Note: this will differ from position whenever the position is changed
    directly by assignment.
    */
    this.newPosition = createVector(_x, _y);
  
    //Position displacement on the x coordinate since the last update
    this.deltaX = 0;
    this.deltaY = 0;
  
    /**
    * The sprite's velocity as a vector (x,y)
    * Velocity is speed broken down to its vertical and horizontal components.
    *
    * @property velocity
    * @type {p5.Vector}
    */
    this.velocity = createVector(0, 0);
  
    /**
    * Set a limit to the sprite's scalar speed regardless of the direction.
    * The value can only be positive. If set to -1, there's no limit.
    *
    * @property maxSpeed
    * @type {Number}
    * @default -1
    */
    this.maxSpeed = -1;
  
    /**
    * Friction factor, reduces the sprite's velocity.
    * The friction should be close to 0 (eg. 0.01)
    * 0: no friction
    * 1: full friction
    *
    * @property friction
    * @type {Number}
    * @default 0
    */
    this.friction = 0;
  
    /**
    * The sprite's current collider.
    * It can either be an Axis Aligned Bounding Box (a non-rotated rectangle)
    * or a circular collider.
    * If the sprite is checked for collision, bounce, overlapping or mouse events the
    * collider is automatically created from the width and height
    * of the sprite or from the image dimension in case of animate sprites
    *
    * You can set a custom collider with Sprite.setCollider
    *
    * @property collider
    * @type {Object}
    */
    this.collider = undefined;
  
    /**
    * Object containing information about the most recent collision/overlapping
    * To be typically used in combination with Sprite.overlap or Sprite.collide
    * functions.
    * The properties are touching.left, touching.right, touching.top,
    * touching.bottom and are either true or false depending on the side of the
    * collider.
    *
    * @property touching
    * @type {Object}
    */
    this.touching = {};
    this.touching.left = false;
    this.touching.right = false;
    this.touching.top = false;
    this.touching.bottom = false;
  
    /**
    * The mass determines the velocity transfer when sprites bounce
    * against each other. See Sprite.bounce
    * The higher the mass the least the sprite will be affected by collisions.
    *
    * @property mass
    * @type {Number}
    * @default 1
    */
    this.mass = 1;
  
    /**
    * If set to true the sprite won't bounce or be displaced by collisions
    * Simulates an infinite mass or an anchored object.
    *
    * @property immovable
    * @type {Boolean}
    * @default false
    */
    this.immovable = false;
  
    //Coefficient of restitution - velocity lost in the bouncing
    //0 perfectly inelastic , 1 elastic, > 1 hyper elastic
  
    /**
    * Coefficient of restitution. The velocity lost after bouncing.
    * 1: perfectly elastic, no energy is lost
    * 0: perfectly inelastic, no bouncing
    * less than 1: inelastic, this is the most common in nature
    * greater than 1: hyper elastic, energy is increased like in a pinball bumper
    *
    * @property restitution
    * @type {Number}
    * @default 1
    */
    this.restitution = 1;
  
    /**
    * Rotation in degrees of the visual element (image or animation)
    * Note: this is not the movement's direction, see getDirection.
    *
    * @property rotation
    * @type {Number}
    * @default 0
    */
    Object.defineProperty(this, 'rotation', {
      enumerable: true,
      get: function() {
        return this._rotation;
      },
      set: function(value) {
        this._rotation = value;
        if (this.rotateToDirection) {
          this.setSpeed(this.getSpeed(), value);
        }
      }
    });
  
    /**
    * Internal rotation variable (expressed in degrees).
    * Note: external callers access this through the rotation property above.
    *
    * @private
    * @property _rotation
    * @type {Number}
    * @default 0
    */
    this._rotation = 0;
  
    /**
    * Rotation change in degrees per frame of thevisual element (image or animation)
    * Note: this is not the movement's direction, see getDirection.
    *
    * @property rotationSpeed
    * @type {Number}
    * @default 0
    */
    this.rotationSpeed = 0;
  
  
    /**
    * Automatically lock the rotation property of the visual element
    * (image or animation) to the sprite's movement direction and vice versa.
    *
    * @property rotateToDirection
    * @type {Boolean}
    * @default false
    */
    this.rotateToDirection = false;
  
  
    /**
    * Determines the rendering order within a group: a sprite with
    * lower depth will appear below the ones with higher depth.
    *
    * Note: drawing a group before another with drawSprites will make
    * its members appear below the second one, like in normal p5 canvas
    * drawing.
    *
    * @property depth
    * @type {Number}
    * @default One more than the greatest existing sprite depth, when calling
    *          createSprite().  When calling new Sprite() directly, depth will
    *          initialize to 0 (not recommended).
    */
    this.depth = 0;
  
    /**
    * Determines the sprite's scale.
    * Example: 2 will be twice the native size of the visuals,
    * 0.5 will be half. Scaling up may make images blurry.
    *
    * @property scale
    * @type {Number}
    * @default 1
    */
    this.scale = 1;
  
    var dirX = 1;
    var dirY = 1;
  
    /**
    * The sprite's visibility.
    *
    * @property visible
    * @type {Boolean}
    * @default true
    */
    this.visible = true;
  
    /**
    * If set to true sprite will track its mouse state.
    * the properties mouseIsPressed and mouseIsOver will be updated.
    * Note: automatically set to true if the functions
    * onMouseReleased or onMousePressed are set.
    *
    * @property mouseActive
    * @type {Boolean}
    * @default false
    */
    this.mouseActive = false;
  
    /**
    * True if mouse is on the sprite's collider.
    * Read only.
    *
    * @property mouseIsOver
    * @type {Boolean}
    */
    this.mouseIsOver = false;
  
    /**
    * True if mouse is pressed on the sprite's collider.
    * Read only.
    *
    * @property mouseIsPressed
    * @type {Boolean}
    */
    this.mouseIsPressed = false;
  
    /*
    * Width of the sprite's current image.
    * If no images or animations are set it's the width of the
    * placeholder rectangle.
    * Used internally to make calculations and draw the sprite.
    *
    * @private
    * @property _internalWidth
    * @type {Number}
    * @default 100
    */
    this._internalWidth = _w;
  
    /*
    * Height of the sprite's current image.
    * If no images or animations are set it's the height of the
    * placeholder rectangle.
    * Used internally to make calculations and draw the sprite.
    *
    * @private
    * @property _internalHeight
    * @type {Number}
    * @default 100
    */
    this._internalHeight = _h;
  
    /*
     * @type {number}
     * @private
     * _horizontalStretch is the value to scale animation sprites in the X direction
     */
    this._horizontalStretch = 1;
  
    /*
     * @type {number}
     * @private
     * _verticalStretch is the value to scale animation sprites in the Y direction
     */
    this._verticalStretch = 1;
  
    /*
     * _internalWidth and _internalHeight are used for all p5.play
     * calculations, but width and height can be extended. For example,
     * you may want users to always get and set a scaled width:
        Object.defineProperty(this, 'width', {
          enumerable: true,
          configurable: true,
          get: function() {
            return this._internalWidth * this.scale;
          },
          set: function(value) {
            this._internalWidth = value / this.scale;
          }
        });
     */
  
    /**
    * Width of the sprite's current image.
    * If no images or animations are set it's the width of the
    * placeholder rectangle.
    *
    * @property width
    * @type {Number}
    * @default 100
    */
    Object.defineProperty(this, 'width', {
      enumerable: true,
      configurable: true,
      get: function() {
        if (this._internalWidth === undefined) {
          return 100;
        } else if (this.animation && pInst._fixedSpriteAnimationFrameSizes) {
          return this._internalWidth * this._horizontalStretch;
        } else {
          return this._internalWidth;
        }
      },
      set: function(value) {
        if (this.animation && pInst._fixedSpriteAnimationFrameSizes) {
          this._horizontalStretch = value / this._internalWidth;
        } else {
          this._internalWidth = value;
        }
      }
    });
  
    if(_w === undefined)
      this.width = 100;
    else
      this.width = _w;
  
    /**
    * Height of the sprite's current image.
    * If no images or animations are set it's the height of the
    * placeholder rectangle.
    *
    * @property height
    * @type {Number}
    * @default 100
    */
    Object.defineProperty(this, 'height', {
      enumerable: true,
      configurable: true,
      get: function() {
        if (this._internalHeight === undefined) {
          return 100;
        } else if (this.animation && pInst._fixedSpriteAnimationFrameSizes) {
          return this._internalHeight * this._verticalStretch;
        } else {
          return this._internalHeight;
        }
      },
      set: function(value) {
        if (this.animation && pInst._fixedSpriteAnimationFrameSizes) {
          this._verticalStretch = value / this._internalHeight;
        } else {
          this._internalHeight = value;
        }
      }
    });
  
    if(_h === undefined)
      this.height = 100;
    else
      this.height = _h;
  
    /**
    * Unscaled width of the sprite
    * If no images or animations are set it's the width of the
    * placeholder rectangle.
    *
    * @property originalWidth
    * @type {Number}
    * @default 100
    */
    this.originalWidth = this._internalWidth;
  
    /**
    * Unscaled height of the sprite
    * If no images or animations are set it's the height of the
    * placeholder rectangle.
    *
    * @property originalHeight
    * @type {Number}
    * @default 100
    */
    this.originalHeight = this._internalHeight;
  
    /**
     * Gets the scaled width of the sprite.
     *
     * @method getScaledWidth
     * @return {Number} Scaled width
     */
    this.getScaledWidth = function() {
      return this.width * this.scale;
    };
  
    /**
     * Gets the scaled height of the sprite.
     *
     * @method getScaledHeight
     * @return {Number} Scaled height
     */
    this.getScaledHeight = function() {
      return this.height * this.scale;
    };
  
    /**
    * True if the sprite has been removed.
    *
    * @property removed
    * @type {Boolean}
    */
    this.removed = false;
  
    /**
    * Cycles before self removal.
    * Set it to initiate a countdown, every draw cycle the property is
    * reduced by 1 unit. At 0 it will call a sprite.remove()
    * Disabled if set to -1.
    *
    * @property life
    * @type {Number}
    * @default -1
    */
    this.life = -1;
  
    /**
    * If set to true, draws an outline of the collider, the depth, and center.
    *
    * @property debug
    * @type {Boolean}
    * @default false
    */
    this.debug = false;
  
    /**
    * If no image or animations are set this is the color of the
    * placeholder rectangle
    *
    * @property shapeColor
    * @type {color}
    */
    this.shapeColor = color(127, 127, 127);
  
    /**
    * Groups the sprite belongs to, including allSprites
    *
    * @property groups
    * @type {Array}
    */
    this.groups = [];
  
    var animations = {};
  
    //The current animation's label.
    var currentAnimation = '';
  
    /**
    * Reference to the current animation.
    *
    * @property animation
    * @type {Animation}
    */
    this.animation = undefined;
  
    /**
     * Swept collider oriented along the current velocity vector, extending to
     * cover the old and new positions of the sprite.
     *
     * The corners of the swept collider will extend beyond the actual swept
     * shape, but it should be sufficient for broad-phase detection of collision
     * candidates.
     *
     * Note that this collider will have no dimensions if the source sprite has no
     * velocity.
     */
    this._sweptCollider = undefined;
  
    /**
    * Sprite x position (alias to position.x).
    *
    * @property x
    * @type {Number}
    */
    Object.defineProperty(this, 'x', {
      enumerable: true,
      get: function() {
        return this.position.x;
      },
      set: function(value) {
        this.position.x = value;
      }
    });
  
    /**
    * Sprite y position (alias to position.y).
    *
    * @property y
    * @type {Number}
    */
    Object.defineProperty(this, 'y', {
      enumerable: true,
      get: function() {
        return this.position.y;
      },
      set: function(value) {
        this.position.y = value;
      }
    });
  
    /**
    * Sprite x velocity (alias to velocity.x).
    *
    * @property velocityX
    * @type {Number}
    */
    Object.defineProperty(this, 'velocityX', {
      enumerable: true,
      get: function() {
        return this.velocity.x;
      },
      set: function(value) {
        this.velocity.x = value;
      }
    });
  
    /**
    * Sprite y velocity (alias to velocity.y).
    *
    * @property velocityY
    * @type {Number}
    */
    Object.defineProperty(this, 'velocityY', {
      enumerable: true,
      get: function() {
        return this.velocity.y;
      },
      set: function(value) {
        this.velocity.y = value;
      }
    });
  
    /**
    * Sprite lifetime (alias to life).
    *
    * @property lifetime
    * @type {Number}
    */
    Object.defineProperty(this, 'lifetime', {
      enumerable: true,
      get: function() {
        return this.life;
      },
      set: function(value) {
        this.life = value;
      }
    });
  
    /**
    * Sprite bounciness (alias to restitution).
    *
    * @property bounciness
    * @type {Number}
    */
    Object.defineProperty(this, 'bounciness', {
      enumerable: true,
      get: function() {
        return this.restitution;
      },
      set: function(value) {
        this.restitution = value;
      }
    });
  
    /**
    * Sprite animation frame delay (alias to animation.frameDelay).
    *
    * @property frameDelay
    * @type {Number}
    */
    Object.defineProperty(this, 'frameDelay', {
      enumerable: true,
      get: function() {
        return this.animation && this.animation.frameDelay;
      },
      set: function(value) {
        if (this.animation) {
          this.animation.frameDelay = value;
        }
      }
    });
  
    /**
     * If the sprite is moving, use the swept collider. Otherwise use the actual
     * collider.
     */
    this._getBroadPhaseCollider = function() {
      return (this.velocity.magSq() > 0) ? this._sweptCollider : this.collider;
    };
  
    /**
     * Returns true if the two sprites crossed paths in the current frame,
     * indicating a possible collision.
     */
    this._doSweptCollidersOverlap = function(target) {
      var displacement = this._getBroadPhaseCollider().collide(target._getBroadPhaseCollider());
      return displacement.x !== 0 || displacement.y !== 0;
    };
  
    /*
     * @private
     * Keep animation properties in sync with how the animation changes.
     */
    this._syncAnimationSizes = function(animations, currentAnimation) {
      if (pInst._fixedSpriteAnimationFrameSizes) {
        return;
      }
      if(animations[currentAnimation].frameChanged || this.width === undefined || this.height === undefined)
      {
        this._internalWidth = animations[currentAnimation].getWidth()*abs(this._getScaleX());
        this._internalHeight = animations[currentAnimation].getHeight()*abs(this._getScaleY());
      }
    };
  
    /**
    * Updates the sprite.
    * Called automatically at the beginning of the draw cycle.
    *
    * @method update
    */
    this.update = function() {
  
      if(!this.removed)
      {
        if (this._sweptCollider && this.velocity.magSq() > 0) {
          this._sweptCollider.updateSweptColliderFromSprite(this);
        }
  
        //if there has been a change somewhere after the last update
        //the old position is the last position registered in the update
        if(this.newPosition !== this.position)
          this.previousPosition = createVector(this.newPosition.x, this.newPosition.y);
        else
          this.previousPosition = createVector(this.position.x, this.position.y);
  
        this.velocity.x *= 1 - this.friction;
        this.velocity.y *= 1 - this.friction;
  
        if(this.maxSpeed !== -1)
          this.limitSpeed(this.maxSpeed);
  
        if(this.rotateToDirection && this.velocity.mag() > 0)
          this._rotation = this.getDirection();
  
        this.rotation += this.rotationSpeed;
  
        this.position.x += this.velocity.x;
        this.position.y += this.velocity.y;
  
        this.newPosition = createVector(this.position.x, this.position.y);
  
        this.deltaX = this.position.x - this.previousPosition.x;
        this.deltaY = this.position.y - this.previousPosition.y;
  
        //if there is an animation
        if(animations[currentAnimation])
        {
          //update it
          animations[currentAnimation].update();
  
          this._syncAnimationSizes(animations, currentAnimation);
        }
  
        //a collider is created either manually with setCollider or
        //when I check this sprite for collisions or overlaps
        if (this.collider) {
          this.collider.updateFromSprite(this);
        }
  
        //mouse actions
        if (this.mouseActive)
        {
          //if no collider set it
            if(!this.collider)
              this.setDefaultCollider();
  
          this.mouseUpdate();
        }
        else
        {
          if (typeof(this.onMouseOver) === 'function' ||
              typeof(this.onMouseOut) === 'function' ||
              typeof(this.onMousePressed) === 'function' ||
              typeof(this.onMouseReleased) === 'function')
          {
            //if a mouse function is set
            //it's implied we want to have it mouse active so
            //we do this automatically
            this.mouseActive = true;
  
            //if no collider set it
            if(!this.collider)
              this.setDefaultCollider();
  
            this.mouseUpdate();
          }
        }
  
        //self destruction countdown
        if (this.life>0)
          this.life--;
        if (this.life === 0)
          this.remove();
      }
    };//end update
  
    /**
     * Creates a default collider matching the size of the
     * placeholder rectangle or the bounding box of the image.
     *
     * @method setDefaultCollider
     */
    this.setDefaultCollider = function() {
      if(animations[currentAnimation] && animations[currentAnimation].getWidth() === 1 && animations[currentAnimation].getHeight() === 1) {
        //animation is still loading
        return;
      }
      this.setCollider('rectangle');
    };
  
    /**
     * Updates the sprite mouse states and triggers the mouse events:
     * onMouseOver, onMouseOut, onMousePressed, onMouseReleased
     *
     * @method mouseUpdate
     */
    this.mouseUpdate = function() {
      var mouseWasOver = this.mouseIsOver;
      var mouseWasPressed = this.mouseIsPressed;
  
      this.mouseIsOver = false;
      this.mouseIsPressed = false;
  
      //rollover
      if(this.collider) {
        var mousePosition;
  
        if(camera.active)
          mousePosition = createVector(camera.mouseX, camera.mouseY);
        else
          mousePosition = createVector(pInst.mouseX, pInst.mouseY);
  
        this.mouseIsOver = this.collider.overlap(new p5.PointCollider(mousePosition));
  
        //global p5 var
        if(this.mouseIsOver && (pInst.mouseIsPressed || pInst.touchIsDown))
          this.mouseIsPressed = true;
  
        //event change - call functions
        if(!mouseWasOver && this.mouseIsOver && this.onMouseOver !== undefined)
          if(typeof(this.onMouseOver) === 'function')
            this.onMouseOver.call(this, this);
          else
            print('Warning: onMouseOver should be a function');
  
        if(mouseWasOver && !this.mouseIsOver && this.onMouseOut !== undefined)
          if(typeof(this.onMouseOut) === 'function')
            this.onMouseOut.call(this, this);
          else
            print('Warning: onMouseOut should be a function');
  
        if(!mouseWasPressed && this.mouseIsPressed && this.onMousePressed !== undefined)
          if(typeof(this.onMousePressed) === 'function')
            this.onMousePressed.call(this, this);
          else
            print('Warning: onMousePressed should be a function');
  
        if(mouseWasPressed && !pInst.mouseIsPressed && !this.mouseIsPressed && this.onMouseReleased !== undefined)
          if(typeof(this.onMouseReleased) === 'function')
            this.onMouseReleased.call(this, this);
          else
            print('Warning: onMouseReleased should be a function');
  
      }
    };
  
    /**
    * Sets a collider for the sprite.
    *
    * In p5.play a Collider is an invisible circle or rectangle
    * that can have any size or position relative to the sprite and which
    * will be used to detect collisions and overlapping with other sprites,
    * or the mouse cursor.
    *
    * If the sprite is checked for collision, bounce, overlapping or mouse events
    * a rectangle collider is automatically created from the width and height
    * parameter passed at the creation of the sprite or the from the image
    * dimension in case of animated sprites.
    *
    * Often the image bounding box is not appropriate as the active area for
    * collision detection so you can set a circular or rectangular sprite with
    * different dimensions and offset from the sprite's center.
    *
    * There are many ways to call this method.  The first argument determines the
    * type of collider you are creating, which in turn changes the remaining
    * arguments.  Valid collider types are:
    *
    * * `point` - A point collider with no dimensions, only a position.
    *
    *   `setCollider("point"[, offsetX, offsetY])`
    *
    * * `circle` - A circular collider with a set radius.
    *
    *   `setCollider("circle"[, offsetX, offsetY[, radius])`
    *
    * * `rectangle` - An alias for `aabb`, below.
    *
    * * `aabb` - An axis-aligned bounding box - has width and height but no rotation.
    *
    *   `setCollider("aabb"[, offsetX, offsetY[, width, height]])`
    *
    * * `obb` - An oriented bounding box - has width, height, and rotation.
    *
    *   `setCollider("obb"[, offsetX, offsetY[, width, height[, rotation]]])`
    *
    *
    * @method setCollider
    * @param {String} type One of "point", "circle", "rectangle", "aabb" or "obb"
    * @param {Number} [offsetX] Collider x position from the center of the sprite
    * @param {Number} [offsetY] Collider y position from the center of the sprite
    * @param {Number} [width] Collider width or radius
    * @param {Number} [height] Collider height
    * @param {Number} [rotation] Collider rotation in degrees
    * @throws {TypeError} if given invalid parameters.
    */
    this.setCollider = function(type, offsetX, offsetY, width, height, rotation) {
      var _type = type ? type.toLowerCase() : '';
      if (_type === 'rectangle') {
        // Map 'rectangle' to AABB.  Change this if you want it to default to OBB.
        _type = 'obb';
      }
  
      // Check correct arguments, provide context-sensitive usage message if wrong.
      if (!(_type === 'point' || _type === 'circle' || _type === 'obb' || _type === 'aabb')) {
        throw new TypeError('setCollider expects the first argument to be one of "point", "circle", "rectangle", "aabb" or "obb"');
      } else if (_type === 'point' && !(arguments.length === 1 || arguments.length === 3)) {
        throw new TypeError('Usage: setCollider("' + type + '"[, offsetX, offsetY])');
      } else if (_type === 'circle' && !(arguments.length === 1 || arguments.length === 3 || arguments.length === 4)) {
        throw new TypeError('Usage: setCollider("' + type + '"[, offsetX, offsetY[, radius]])');
      } else if (_type === 'aabb' && !(arguments.length === 1 || arguments.length === 3 || arguments.length === 5)) {
        throw new TypeError('Usage: setCollider("' + type + '"[, offsetX, offsetY[, width, height]])');
      } else if (_type === 'obb' && !(arguments.length === 1 || arguments.length === 3 || arguments.length === 5 || arguments.length === 6)) {
        throw new TypeError('Usage: setCollider("' + type + '"[, offsetX, offsetY[, width, height[, rotation]]])');
      }
  
      //var center = this.position;
      var offset = createVector(offsetX, offsetY);
  
      if (_type === 'point') {
        this.collider = p5.PointCollider.createFromSprite(this, offset);
      } else if (_type === 'circle') {
        this.collider = p5.CircleCollider.createFromSprite(this, offset, width);
      } else if (_type === 'aabb') {
        this.collider = p5.AxisAlignedBoundingBoxCollider.createFromSprite(this, offset, width, height);
      } else if (_type === 'obb') {
        this.collider = p5.OrientedBoundingBoxCollider.createFromSprite(this, offset, width, height, radians(rotation));
      }
  
      this._sweptCollider = new p5.OrientedBoundingBoxCollider();
  
      // Disabled for Code.org, since perf seems better without the quadtree:
      // quadTree.insert(this);
    };
  
    /**
    * Sets the sprite's horizontal mirroring.
    * If 1 the images displayed normally
    * If -1 the images are flipped horizontally
    * If no argument returns the current x mirroring
    *
    * @method mirrorX
    * @param {Number} dir Either 1 or -1
    * @return {Number} Current mirroring if no parameter is specified
    */
    this.mirrorX = function(dir) {
      if(dir === 1 || dir === -1)
        dirX = dir;
      else
        return dirX;
    };
  
    /**
    * Sets the sprite's vertical mirroring.
    * If 1 the images displayed normally
    * If -1 the images are flipped vertically
    * If no argument returns the current y mirroring
    *
    * @method mirrorY
    * @param {Number} dir Either 1 or -1
    * @return {Number} Current mirroring if no parameter is specified
    */
    this.mirrorY = function(dir) {
      if(dir === 1 || dir === -1)
        dirY = dir;
      else
        return dirY;
    };
  
    /*
     * Returns the value the sprite should be scaled in the X direction.
     * Used to calculate rendering and collisions.
     * When _fixedSpriteAnimationFrameSizes is set, the scale value should
     * include the horizontal stretch for animations.
     * @private
     */
    this._getScaleX = function()
    {
      if (pInst._fixedSpriteAnimationFrameSizes) {
        return this.scale * this._horizontalStretch;
      }
      return this.scale;
    };
  
    /*
     * Returns the value the sprite should be scaled in the Y direction.
     * Used to calculate rendering and collisions.
     * When _fixedSpriteAnimationFrameSizes is set, the scale value should
     * include the vertical stretch for animations.
     * @private
     */
    this._getScaleY = function()
    {
      if (pInst._fixedSpriteAnimationFrameSizes) {
        return this.scale * this._verticalStretch;
      }
      return this.scale;
    };
  
    /**
     * Manages the positioning, scale and rotation of the sprite
     * Called automatically, it should not be overridden
     * @private
     * @final
     * @method display
     */
    this.display = function()
    {
      if (this.visible && !this.removed)
      {
        push();
        colorMode(RGB);
  
        noStroke();
        rectMode(CENTER);
        ellipseMode(CENTER);
        imageMode(CENTER);
  
        translate(this.position.x, this.position.y);
        if (pInst._angleMode === pInst.RADIANS) {
          rotate(radians(this.rotation));
        } else {
          rotate(this.rotation);
        }
        scale(this._getScaleX()*dirX, this._getScaleY()*dirY);
        this.draw();
        //draw debug info
        pop();
  
  
        if(this.debug)
        {
          push();
          //draw the anchor point
          stroke(0, 255, 0);
          strokeWeight(1);
          line(this.position.x-10, this.position.y, this.position.x+10, this.position.y);
          line(this.position.x, this.position.y-10, this.position.x, this.position.y+10);
          noFill();
  
          //depth number
          noStroke();
          fill(0, 255, 0);
          textAlign(LEFT, BOTTOM);
          textSize(16);
          text(this.depth+'', this.position.x+4, this.position.y-2);
  
          noFill();
          stroke(0, 255, 0);
  
          // Draw collision shape
          if (this.collider === undefined) {
            this.setDefaultCollider();
          }
          if(this.collider) {
            this.collider.draw(pInst);
          }
          pop();
        }
  
      }
    };
  
  
    /**
    * Manages the visuals of the sprite.
    * It can be overridden with a custom drawing function.
    * The 0,0 point will be the center of the sprite.
    * Example:
    * sprite.draw = function() { ellipse(0,0,10,10) }
    * Will display the sprite as circle.
    *
    * @method draw
    */
    this.draw = function()
    {
      if(currentAnimation !== '' && animations)
      {
        if(animations[currentAnimation]) {
          if(this.tint) {
            push();
            tint(this.tint);
          }
          animations[currentAnimation].draw(0, 0, 0);
          if(this.tint) {
            pop();
          }
        }
      }
      else
      {
        var fillColor = this.shapeColor;
        if (this.tint) {
          fillColor = lerpColor(color(fillColor), color(this.tint), 0.5);
        }
        noStroke();
        fill(fillColor);
        rect(0, 0, this._internalWidth, this._internalHeight);
      }
    };
  
    /**
     * Removes the Sprite from the sketch.
     * The removed Sprite won't be drawn or updated anymore.
     *
     * @method remove
     */
    this.remove = function() {
      this.removed = true;
  
      quadTree.removeObject(this);
  
      //when removed from the "scene" also remove all the references in all the groups
      while (this.groups.length > 0) {
        this.groups[0].remove(this);
      }
    };
  
    /**
     * Alias for <a href='#method-remove'>remove()</a>
     *
     * @method destroy
     */
    this.destroy = this.remove;
  
    /**
    * Sets the velocity vector.
    *
    * @method setVelocity
    * @param {Number} x X component
    * @param {Number} y Y component
    */
    this.setVelocity = function(x, y) {
      this.velocity.x = x;
      this.velocity.y = y;
    };
  
    /**
    * Calculates the scalar speed.
    *
    * @method getSpeed
    * @return {Number} Scalar speed
    */
    this.getSpeed = function() {
      return this.velocity.mag();
    };
  
    /**
    * Calculates the movement's direction in degrees.
    *
    * @method getDirection
    * @return {Number} Angle in degrees
    */
    this.getDirection = function() {
  
      var direction = atan2(this.velocity.y, this.velocity.x);
  
      if(isNaN(direction))
        direction = 0;
  
      // Unlike Math.atan2, the atan2 method above will return degrees if
      // the current p5 angleMode is DEGREES, and radians if the p5 angleMode is
      // RADIANS.  This method should always return degrees (for now).
      // See https://github.com/molleindustria/p5.play/issues/94
      if (pInst._angleMode === pInst.RADIANS) {
        direction = degrees(direction);
      }
  
      return direction;
    };
  
    /**
    * Adds the sprite to an existing group
    *
    * @method addToGroup
    * @param {Object} group
    */
    this.addToGroup = function(group) {
      if(group instanceof Array)
        group.add(this);
      else
        print('addToGroup error: '+group+' is not a group');
    };
  
    /**
    * Limits the scalar speed.
    *
    * @method limitSpeed
    * @param {Number} max Max speed: positive number
    */
    this.limitSpeed = function(max) {
  
      //update linear speed
      var speed = this.getSpeed();
  
      if(abs(speed)>max)
      {
        //find reduction factor
        var k = max/abs(speed);
        this.velocity.x *= k;
        this.velocity.y *= k;
      }
    };
  
    /**
    * Set the speed and direction of the sprite.
    * The action overwrites the current velocity.
    * If direction is not supplied, the current direction is maintained.
    * If direction is not supplied and there is no current velocity, the current
    * rotation angle used for the direction.
    *
    * @method setSpeed
    * @param {Number}  speed Scalar speed
    * @param {Number}  [angle] Direction in degrees
    */
    this.setSpeed = function(speed, angle) {
      var a;
      if (typeof angle === 'undefined') {
        if (this.velocity.x !== 0 || this.velocity.y !== 0) {
          a = pInst.atan2(this.velocity.y, this.velocity.x);
        } else {
          if (pInst._angleMode === pInst.RADIANS) {
            a = radians(this._rotation);
          } else {
            a = this._rotation;
          }
        }
      } else {
        if (pInst._angleMode === pInst.RADIANS) {
          a = radians(angle);
        } else {
          a = angle;
        }
      }
      this.velocity.x = cos(a)*speed;
      this.velocity.y = sin(a)*speed;
    };
  
    /**
     * Alias for <a href='#method-setSpeed'>setSpeed()</a>
     *
     * @method setSpeedAndDirection
     * @param {Number}  speed Scalar speed
     * @param {Number}  [angle] Direction in degrees
     */
    this.setSpeedAndDirection = this.setSpeed;
  
    /**
    * Alias for <a href='Animation.html#method-changeFrame'>animation.changeFrame()</a>
    *
    * @method setFrame
    * @param {Number} frame Frame number (starts from 0).
    */
    this.setFrame = function(f) {
      if (this.animation) {
        this.animation.changeFrame(f);
      }
    };
  
    /**
    * Alias for <a href='Animation.html#method-nextFrame'>animation.nextFrame()</a>
    *
    * @method nextFrame
    */
    this.nextFrame = function() {
      if (this.animation) {
        this.animation.nextFrame();
      }
    };
  
    /**
    * Alias for <a href='Animation.html#method-previousFrame'>animation.previousFrame()</a>
    *
    * @method previousFrame
    */
    this.previousFrame = function() {
      if (this.animation) {
        this.animation.previousFrame();
      }
    };
  
    /**
    * Alias for <a href='Animation.html#method-stop'>animation.stop()</a>
    *
    * @method pause
    */
    this.pause = function() {
      if (this.animation) {
        this.animation.stop();
      }
    };
  
    /**
     * Alias for <a href='Animation.html#method-play'>animation.play()</a> with extra logic
     *
     * Plays/resumes the sprite's current animation.
     * If the animation is currently playing this has no effect.
     * If the animation has stopped at its last frame, this will start it over
     * at the beginning.
     *
     * @method play
     */
    this.play = function() {
      if (!this.animation) {
        return;
      }
      // Normally this just sets the 'playing' flag without changing the animation
      // frame, which will cause the animation to continue on the next update().
      // If the animation is non-looping and is stopped at the last frame
      // we also rewind the animation to the beginning.
      if (!this.animation.looping && !this.animation.playing && this.animation.getFrame() === this.animation.images.length - 1) {
        this.animation.rewind();
      }
      this.animation.play();
    };
  
    /**
     * Wrapper to access <a href='Animation.html#prop-frameChanged'>animation.frameChanged</a>
     *
     * @method frameDidChange
     * @return {Boolean} true if the animation frame has changed
     */
    this.frameDidChange = function() {
      return this.animation ? this.animation.frameChanged : false;
    };
  
    /**
    * Rotate the sprite towards a specific position
    *
    * @method setFrame
    * @param {Number} x Horizontal coordinate to point to
    * @param {Number} y Vertical coordinate to point to
    */
    this.pointTo = function(x, y) {
      var yDelta = y - this.position.y;
      var xDelta = x - this.position.x;
      if (!isNaN(xDelta) && !isNaN(yDelta) && (xDelta !== 0 || yDelta !== 0)) {
        var radiansAngle = Math.atan2(yDelta, xDelta);
        this.rotation = 360 * radiansAngle / (2 * Math.PI);
      }
    };
  
    /**
    * Pushes the sprite in a direction defined by an angle.
    * The force is added to the current velocity.
    *
    * @method addSpeed
    * @param {Number}  speed Scalar speed to add
    * @param {Number}  angle Direction in degrees
    */
    this.addSpeed = function(speed, angle) {
      var a;
      if (pInst._angleMode === pInst.RADIANS) {
        a = radians(angle);
      } else {
        a = angle;
      }
      this.velocity.x += cos(a) * speed;
      this.velocity.y += sin(a) * speed;
    };
  
    /**
    * Pushes the sprite toward a point.
    * The force is added to the current velocity.
    *
    * @method attractionPoint
    * @param {Number}  magnitude Scalar speed to add
    * @param {Number}  pointX Direction x coordinate
    * @param {Number}  pointY Direction y coordinate
    */
    this.attractionPoint = function(magnitude, pointX, pointY) {
      var angle = atan2(pointY-this.position.y, pointX-this.position.x);
      this.velocity.x += cos(angle) * magnitude;
      this.velocity.y += sin(angle) * magnitude;
    };
  
  
    /**
    * Adds an image to the sprite.
    * An image will be considered a one-frame animation.
    * The image should be preloaded in the preload() function using p5 loadImage.
    * Animations require a identifying label (string) to change them.
    * The image is stored in the sprite but not necessarily displayed
    * until Sprite.changeAnimation(label) is called
    *
    * Usages:
    * - sprite.addImage(label, image);
    * - sprite.addImage(image);
    *
    * If only an image is passed no label is specified
    *
    * @method addImage
    * @param {String|p5.Image} label Label or image
    * @param {p5.Image} [img] Image
    */
    this.addImage = function()
    {
      if(typeof arguments[0] === 'string' && arguments[1] instanceof p5.Image)
        this.addAnimation(arguments[0], arguments[1]);
      else if(arguments[0] instanceof p5.Image)
        this.addAnimation('normal', arguments[0]);
      else
        throw('addImage error: allowed usages are <image> or <label>, <image>');
    };
  
    /**
    * Adds an animation to the sprite.
    * The animation should be preloaded in the preload() function
    * using loadAnimation.
    * Animations require a identifying label (string) to change them.
    * Animations are stored in the sprite but not necessarily displayed
    * until Sprite.changeAnimation(label) is called.
    *
    * Usage:
    * - sprite.addAnimation(label, animation);
    *
    * Alternative usages. See Animation for more information on file sequences:
    * - sprite.addAnimation(label, firstFrame, lastFrame);
    * - sprite.addAnimation(label, frame1, frame2, frame3...);
    *
    * @method addAnimation
    * @param {String} label Animation identifier
    * @param {Animation} animation The preloaded animation
    */
    this.addAnimation = function(label)
    {
      var anim;
  
      if(typeof label !== 'string')
      {
        print('Sprite.addAnimation error: the first argument must be a label (String)');
        return -1;
      }
      else if(arguments.length < 2)
      {
        print('addAnimation error: you must specify a label and n frame images');
        return -1;
      }
      else if(arguments[1] instanceof Animation)
      {
  
        var sourceAnimation = arguments[1];
  
        var newAnimation = sourceAnimation.clone();
  
        animations[label] = newAnimation;
  
        if(currentAnimation === '')
        {
          currentAnimation = label;
          this.animation = newAnimation;
        }
  
        newAnimation.isSpriteAnimation = true;
  
        this._internalWidth = newAnimation.getWidth()*abs(this._getScaleX());
        this._internalHeight = newAnimation.getHeight()*abs(this._getScaleY());
  
        return newAnimation;
      }
      else
      {
        var animFrames = [];
        for(var i=1; i<arguments.length; i++)
          animFrames.push(arguments[i]);
  
        anim = construct(pInst.Animation, animFrames);
        animations[label] = anim;
  
        if(currentAnimation === '')
        {
          currentAnimation = label;
          this.animation = anim;
        }
        anim.isSpriteAnimation = true;
  
        this._internalWidth = anim.getWidth()*abs(this._getScaleX());
        this._internalHeight = anim.getHeight()*abs(this._getScaleY());
  
        return anim;
      }
  
    };
  
    /**
    * Changes the displayed image/animation.
    * Equivalent to changeAnimation
    *
    * @method changeImage
    * @param {String} label Image/Animation identifier
    */
    this.changeImage = function(label) {
      this.changeAnimation(label);
    };
  
     /**
    * Returns the label of the current animation
    *
    * @method getAnimationLabel
    * @return {String} label Image/Animation identifier
    */
    this.getAnimationLabel = function() {
      return currentAnimation;
    };
  
    /**
    * Changes the displayed animation.
    * See Animation for more control over the sequence.
    *
    * @method changeAnimation
    * @param {String} label Animation identifier
    */
    this.changeAnimation = function(label) {
      if(!animations[label])
        print('changeAnimation error: no animation labeled '+label);
      else
      {
        currentAnimation = label;
        this.animation = animations[label];
      }
    };
  
    /**
    * Sets the animation from a list in _predefinedSpriteAnimations.
    *
    * @method setAnimation
    * @private
    * @param {String} label Animation identifier
    */
    this.setAnimation = function(animationName) {
      if (animationName === this.getAnimationLabel()) {
        return;
      }
  
      var animation = pInst._predefinedSpriteAnimations &&
          pInst._predefinedSpriteAnimations[animationName];
      if (typeof animation === 'undefined') {
        throw new Error('Unable to find an animation named "' + animationName +
            '".  Please make sure the animation exists.');
      }
      this.addAnimation(animationName, animation);
      this.changeAnimation(animationName);
      if (pInst._pauseSpriteAnimationsByDefault) {
        this.pause();
      }
    };
  
    /**
    * Checks if the given point corresponds to a transparent pixel
    * in the sprite's current image. It can be used to check a point collision
    * against only the visible part of the sprite.
    *
    * @method overlapPixel
    * @param {Number} pointX x coordinate of the point to check
    * @param {Number} pointY y coordinate of the point to check
    * @return {Boolean} result True if non-transparent
    */
    this.overlapPixel = function(pointX, pointY) {
      var point = createVector(pointX, pointY);
  
      var img = this.animation.getFrameImage();
  
      //convert point to img relative position
      point.x -= this.position.x-img.width/2;
      point.y -= this.position.y-img.height/2;
  
      //out of the image entirely
      if(point.x<0 || point.x>img.width || point.y<0 || point.y>img.height)
        return false;
      else if(this.rotation === 0 && this.scale === 1)
      {
        //true if full opacity
        var values = img.get(point.x, point.y);
        return values[3] === 255;
      }
      else
      {
        print('Error: overlapPixel doesn\'t work with scaled or rotated sprites yet');
        //offscreen printing to be implemented bleurch
        return false;
      }
    };
  
    /**
    * Checks if the given point is inside the sprite's collider.
    *
    * @method overlapPoint
    * @param {Number} pointX x coordinate of the point to check
    * @param {Number} pointY y coordinate of the point to check
    * @return {Boolean} result True if inside
    */
    this.overlapPoint = function(pointX, pointY) {
      if(!this.collider)
        this.setDefaultCollider();
  
      if(this.collider) {
        var point = new p5.PointCollider(new p5.Vector(pointX, pointY));
        return this.collider.overlap(point);
      }
      return false;
    };
  
  
    /**
    * Checks if the the sprite is overlapping another sprite or a group.
    * The check is performed using the colliders. If colliders are not set
    * they will be created automatically from the image/animation bounding box.
    *
    * A callback function can be specified to perform additional operations
    * when the overlap occours.
    * If the target is a group the function will be called for each single
    * sprite overlapping. The parameter of the function are respectively the
    * current sprite and the colliding sprite.
    *
    * @example
    *     sprite.overlap(otherSprite, explosion);
    *
    *     function explosion(spriteA, spriteB) {
    *       spriteA.remove();
    *       spriteB.score++;
    *     }
    *
    * @method overlap
    * @param {Object} target Sprite or group to check against the current one
    * @param {Function} [callback] The function to be called if overlap is positive
    * @return {Boolean} True if overlapping
    */
    this.overlap = function(target, callback) {
      return this._collideWith('overlap', target, callback);
    };
  
    /**
     * Alias for <a href='#method-overlap'>overlap()</a>, except without a
     * callback parameter.
     * The check is performed using the colliders. If colliders are not set
     * they will be created automatically from the image/animation bounding box.
     *
     * Returns whether or not this sprite is overlapping another sprite
     * or group. Modifies the sprite's touching property object.
     *
     * @method isTouching
     * @param {Object} target Sprite or group to check against the current one
     * @return {Boolean} True if touching
     */
    this.isTouching = this.overlap;
  
    /**
    * Checks if the the sprite is overlapping another sprite or a group.
    * If the overlap is positive the sprite will bounce with the target(s)
    * treated as immovable with a restitution coefficient of zero.
    *
    * The check is performed using the colliders. If colliders are not set
    * they will be created automatically from the image/animation bounding box.
    *
    * A callback function can be specified to perform additional operations
    * when the collision occours.
    * If the target is a group the function will be called for each single
    * sprite colliding. The parameter of the function are respectively the
    * current sprite and the colliding sprite.
    *
    * @example
    *     sprite.collide(otherSprite, explosion);
    *
    *     function explosion(spriteA, spriteB) {
    *       spriteA.remove();
    *       spriteB.score++;
    *     }
    *
    * @method collide
    * @param {Object} target Sprite or group to check against the current one
    * @param {Function} [callback] The function to be called if overlap is positive
    * @return {Boolean} True if overlapping
    */
    this.collide = function(target, callback) {
      return this._collideWith('collide', target, callback);
    };
  
    /**
    * Checks if the the sprite is overlapping another sprite or a group.
    * If the overlap is positive the current sprite will displace
    * the colliding one to the closest non-overlapping position.
    *
    * The check is performed using the colliders. If colliders are not set
    * they will be created automatically from the image/animation bounding box.
    *
    * A callback function can be specified to perform additional operations
    * when the collision occours.
    * If the target is a group the function will be called for each single
    * sprite colliding. The parameter of the function are respectively the
    * current sprite and the colliding sprite.
    *
    * @example
    *     sprite.displace(otherSprite, explosion);
    *
    *     function explosion(spriteA, spriteB) {
    *       spriteA.remove();
    *       spriteB.score++;
    *     }
    *
    * @method displace
    * @param {Object} target Sprite or group to check against the current one
    * @param {Function} [callback] The function to be called if overlap is positive
    * @return {Boolean} True if overlapping
    */
    this.displace = function(target, callback) {
      return this._collideWith('displace', target, callback);
    };
  
    /**
    * Checks if the the sprite is overlapping another sprite or a group.
    * If the overlap is positive the sprites will bounce affecting each
    * other's trajectories depending on their .velocity, .mass and .restitution
    *
    * The check is performed using the colliders. If colliders are not set
    * they will be created automatically from the image/animation bounding box.
    *
    * A callback function can be specified to perform additional operations
    * when the collision occours.
    * If the target is a group the function will be called for each single
    * sprite colliding. The parameter of the function are respectively the
    * current sprite and the colliding sprite.
    *
    * @example
    *     sprite.bounce(otherSprite, explosion);
    *
    *     function explosion(spriteA, spriteB) {
    *       spriteA.remove();
    *       spriteB.score++;
    *     }
    *
    * @method bounce
    * @param {Object} target Sprite or group to check against the current one
    * @param {Function} [callback] The function to be called if overlap is positive
    * @return {Boolean} True if overlapping
    */
    this.bounce = function(target, callback) {
      return this._collideWith('bounce', target, callback);
    };
  
    /**
    * Checks if the the sprite is overlapping another sprite or a group.
    * If the overlap is positive the sprite will bounce with the target(s)
    * treated as immovable.
    *
    * The check is performed using the colliders. If colliders are not set
    * they will be created automatically from the image/animation bounding box.
    *
    * A callback function can be specified to perform additional operations
    * when the collision occours.
    * If the target is a group the function will be called for each single
    * sprite colliding. The parameter of the function are respectively the
    * current sprite and the colliding sprite.
    *
    * @example
    *     sprite.bounceOff(otherSprite, explosion);
    *
    *     function explosion(spriteA, spriteB) {
    *       spriteA.remove();
    *       spriteB.score++;
    *     }
    *
    * @method bounceOff
    * @param {Object} target Sprite or group to check against the current one
    * @param {Function} [callback] The function to be called if overlap is positive
    * @return {Boolean} True if overlapping
    */
    this.bounceOff = function(target, callback) {
      return this._collideWith('bounceOff', target, callback);
    };
  
    /**
     * Internal collision detection function. Do not use directly.
     *
     * Handles collision with individual sprites or with groups, using the
     * quadtree to optimize the latter.
     *
     * @method _collideWith
     * @private
     * @param {string} type - 'overlap', 'isTouching', 'displace', 'collide',
     *   'bounce' or 'bounceOff'
     * @param {Sprite|Group} target
     * @param {function} callback - if collision occurred (ignored for 'isTouching')
     * @return {boolean} true if a collision occurred
     */
    this._collideWith = function(type, target, callback) {
      this.touching.left = false;
      this.touching.right = false;
      this.touching.top = false;
      this.touching.bottom = false;
  
      if (this.removed) {
        return false;
      }
  
      var others = [];
  
      if (target instanceof Sprite) {
        others.push(target);
      } else if (target instanceof Array) {
        if (pInst.quadTree !== undefined && pInst.quadTree.active) {
          others = pInst.quadTree.retrieveFromGroup(this, target);
        }
  
        // If the quadtree is disabled -or- no sprites in this group are in the
        // quadtree yet (because their default colliders haven't been created)
        // we should just check all of them.
        if (others.length === 0) {
          others = target;
        }
      } else {
        throw('Error: overlap can only be checked between sprites or groups');
      }
  
      var result = false;
      for(var i = 0; i < others.length; i++) {
        result = this._collideWithOne(type, others[i], callback) || result;
      }
      return result;
    };
  
    /**
     * Helper collision method for colliding this sprite with one other sprite.
     *
     * Has the side effect of setting this.touching properties to TRUE if collisions
     * occur.
     *
     * @method _collideWithOne
     * @private
     * @param {string} type - 'overlap', 'isTouching', 'displace', 'collide',
     *   'bounce' or 'bounceOff'
     * @param {Sprite} other
     * @param {function} callback - if collision occurred (ignored for 'isTouching')
     * @return {boolean} true if a collision occurred
     */
    this._collideWithOne = function(type, other, callback) {
      // Never collide with self
      if (other === this || other.removed) {
        return false;
      }
  
      if (this.collider === undefined) {
        this.setDefaultCollider();
      }
  
      if (other.collider === undefined) {
        other.setDefaultCollider();
      }
  
      if (!this.collider || !other.collider) {
        // We were unable to create a collider for one of the sprites.
        // This usually means its animation is not available yet; it will be soon.
        // Don't collide for now.
        return false;
      }
  
      // Actually compute the overlap of the two colliders
      var displacement = this._findDisplacement(other);
      if (displacement.x === 0 && displacement.y === 0) {
        // These sprites are not overlapping.
        return false;
      }
  
      if (displacement.x > 0)
        this.touching.left = true;
      if (displacement.x < 0)
        this.touching.right = true;
      if (displacement.y < 0)
        this.touching.bottom = true;
      if (displacement.y > 0)
        this.touching.top = true;
  
      // Apply displacement out of collision
      if (type === 'displace' && !other.immovable) {
        other.position.sub(displacement);
      } else if ((type === 'collide' || type === 'bounce' || type === 'bounceOff') && !this.immovable) {
        this.position.add(displacement);
        this.previousPosition = createVector(this.position.x, this.position.y);
        this.newPosition = createVector(this.position.x, this.position.y);
        this.collider.updateFromSprite(this);
      }
  
      // Create special behaviors for certain collision types by temporarily
      // overriding type and sprite properties.
      // See another block near the end of this method that puts them back.
      var originalType = type;
      var originalThisImmovable = this.immovable;
      var originalOtherImmovable = other.immovable;
      var originalOtherRestitution = other.restitution;
      if (originalType === 'collide') {
        type = 'bounce';
        other.immovable = true;
        other.restitution = 0;
      } else if (originalType === 'bounceOff') {
        type = 'bounce';
        other.immovable = true;
      }
  
      // If this is a 'bounce' collision, determine the new velocities for each sprite
      if (type === 'bounce') {
        // We are concerned only with velocities parallel to the collision normal,
        // so project our sprite velocities onto that normal (captured in the
        // displacement vector) and use these throughout the calculation
        var thisInitialVelocity = p5.Vector.project(this.velocity, displacement);
        var otherInitialVelocity = p5.Vector.project(other.velocity, displacement);
  
        // We only care about relative mass values, so if one of the sprites
        // is considered 'immovable' treat the _other_ sprite's mass as zero
        // to get the correct results.
        var thisMass = this.mass;
        var otherMass = other.mass;
        if (this.immovable) {
          thisMass = 1;
          otherMass = 0;
        } else if (other.immovable) {
          thisMass = 0;
          otherMass = 1;
        }
  
        var combinedMass = thisMass + otherMass;
        var coefficientOfRestitution = this.restitution * other.restitution;
        var initialMomentum = p5.Vector.add(
          p5.Vector.mult(thisInitialVelocity, thisMass),
          p5.Vector.mult(otherInitialVelocity, otherMass)
        );
        var thisFinalVelocity = p5.Vector.sub(otherInitialVelocity, thisInitialVelocity)
          .mult(otherMass * coefficientOfRestitution)
          .add(initialMomentum)
          .div(combinedMass);
        var otherFinalVelocity = p5.Vector.sub(thisInitialVelocity, otherInitialVelocity)
          .mult(thisMass * coefficientOfRestitution)
          .add(initialMomentum)
          .div(combinedMass);
        // Remove velocity before and apply velocity after to both members.
        this.velocity.sub(thisInitialVelocity).add(thisFinalVelocity);
        other.velocity.sub(otherInitialVelocity).add(otherFinalVelocity);
      }
  
      // Restore sprite properties now that velocity changes have been made.
      // See another block before velocity changes that sets these up.
      type = originalType;
      this.immovable = originalThisImmovable;
      other.immovable = originalOtherImmovable;
      other.restitution = originalOtherRestitution;
  
      // Finally, for all collision types except 'isTouching', call the callback
      // and record that collision occurred.
      if (typeof callback === 'function' && type !== 'isTouching') {
        callback.call(this, this, other);
      }
      return true;
    };
  
    this._findDisplacement = function(target) {
      // Multisample if tunneling occurs:
      // Do broad-phase detection. Check if the swept colliders overlap.
      // In that case, test interpolations between their last positions and their
      // current positions, and check for tunneling that way.
      // Use multisampling to catch collisions we might otherwise miss.
      if (this._doSweptCollidersOverlap(target)) {
        // Figure out how many samples we should take.
        // We want to limit this so that we don't take an absurd number of samples
        // when objects end up at very high velocities (as happens sometimes in
        // game engines).
        var radiusOnVelocityAxis = Math.max(
          this.collider._getMinRadius(),
          target.collider._getMinRadius());
        var relativeVelocity = p5.Vector.sub(this.velocity, target.velocity).mag();
        var timestep = Math.max(0.015, radiusOnVelocityAxis / relativeVelocity);
        // If the objects are small enough to benefit from multisampling at this
        // relative velocity
        if (timestep < 1) {
          // Move sprites back to previous positions
          // (We jump through some hoops here to avoid creating too many new
          //  vector objects)
          var thisOriginalPosition = this.position.copy();
          var targetOriginalPosition = target.position.copy();
          this.position.set(this.previousPosition);
          target.position.set(target.previousPosition);
  
          // Scale deltas down to timestep-deltas
          var thisDelta = p5.Vector.sub(thisOriginalPosition, this.previousPosition).mult(timestep);
          var targetDelta = p5.Vector.sub(targetOriginalPosition, target.previousPosition).mult(timestep);
  
          // Note: We don't have to check the original position, we can assume it's
          // non-colliding (or it would have been handled on the last frame).
          for (var i = timestep; i < 1; i += timestep) {
            // Move the sprites forward by the sub-frame timestep
            this.position.add(thisDelta);
            target.position.add(targetDelta);
            this.collider.updateFromSprite(this);
            target.collider.updateFromSprite(target);
  
            // Check for collision at the new sub-frame position
            var displacement = this.collider.collide(target.collider);
            if (displacement.x !== 0 || displacement.y !== 0) {
              // These sprites are overlapping - we have a displacement, and a
              // point-in-time for the collision.
              // If either sprite is immovable, it should move back to its final
              // position.  Otherwise, leave the sprites at their interpolated
              // position when the collision occurred.
              if (this.immovable) {
                this.position.set(thisOriginalPosition);
              }
  
              if (target.immovable) {
                target.position.set(targetOriginalPosition);
              }
  
              return displacement;
            }
          }
  
          // If we didn't find a displacement partway through,
          // restore the sprites to their original positions and fall through
          // to do the collision check at their final position.
          this.position.set(thisOriginalPosition);
          target.position.set(targetOriginalPosition);
        }
      }
  
      // Ensure the colliders are properly updated to match their parent
      // sprites. Maybe someday we won't have to do this, but for now
      // sprites aren't guaranteed to be internally consistent we do a
      // last-minute update to make sure.
      this.collider.updateFromSprite(this);
      target.collider.updateFromSprite(target);
  
      return this.collider.collide(target.collider);
    };
  } //end Sprite class
  
  defineLazyP5Property('Sprite', boundConstructorFactory(Sprite));
  
  /**
     * A camera facilitates scrolling and zooming for scenes extending beyond
     * the canvas. A camera has a position, a zoom factor, and the mouse
     * coordinates relative to the view.
     * The camera is automatically created on the first draw cycle.
     *
     * In p5.js terms the camera wraps the whole drawing cycle in a
     * transformation matrix but it can be disable anytime during the draw
     * cycle for example to draw interface elements in an absolute position.
     *
     * @class Camera
     * @constructor
     * @param {Number} x Initial x coordinate
     * @param {Number} y Initial y coordinate
     * @param {Number} zoom magnification
     **/
  function Camera(pInst, x, y, zoom) {
    /**
    * Camera position. Defines the global offset of the sketch.
    *
    * @property position
    * @type {p5.Vector}
    */
    this.position = pInst.createVector(x, y);
  
    /**
    * Camera x position. Defines the horizontal global offset of the sketch.
    *
    * @property x
    * @type {Number}
    */
    Object.defineProperty(this, 'x', {
      enumerable: true,
      get: function() {
        return this.position.x;
      },
      set: function(value) {
        this.position.x = value;
      }
    });
  
    /**
    * Camera y position. Defines the horizontal global offset of the sketch.
    *
    * @property y
    * @type {Number}
    */
    Object.defineProperty(this, 'y', {
      enumerable: true,
      get: function() {
        return this.position.y;
      },
      set: function(value) {
        this.position.y = value;
      }
    });
  
    /**
    * Camera zoom. Defines the global scale of the sketch.
    * A scale of 1 will be the normal size. Setting it to 2 will make everything
    * twice the size. .5 will make everything half size.
    *
    * @property zoom
    * @type {Number}
    */
    this.zoom = zoom;
  
    /**
    * MouseX translated to the camera view.
    * Offsetting and scaling the canvas will not change the sprites' position
    * nor the mouseX and mouseY variables. Use this property to read the mouse
    * position if the camera moved or zoomed.
    *
    * @property mouseX
    * @type {Number}
    */
    this.mouseX = pInst.mouseX;
  
    /**
    * MouseY translated to the camera view.
    * Offsetting and scaling the canvas will not change the sprites' position
    * nor the mouseX and mouseY variables. Use this property to read the mouse
    * position if the camera moved or zoomed.
    *
    * @property mouseY
    * @type {Number}
    */
    this.mouseY = pInst.mouseY;
  
    /**
    * True if the camera is active.
    * Read only property. Use the methods Camera.on() and Camera.off()
    * to enable or disable the camera.
    *
    * @property active
    * @type {Boolean}
    */
    this.active = false;
  
    /**
    * Check to see if the camera is active.
    * Use the methods Camera.on() and Camera.off()
    * to enable or disable the camera.
    *
    * @method isActive
    * @return {Boolean} true if the camera is active
    */
    this.isActive = function() {
      return this.active;
    };
  
    /**
    * Activates the camera.
    * The canvas will be drawn according to the camera position and scale until
    * Camera.off() is called
    *
    * @method on
    */
    this.on = function() {
      if(!this.active)
      {
        cameraPush.call(pInst);
        this.active = true;
      }
    };
  
    /**
    * Deactivates the camera.
    * The canvas will be drawn normally, ignoring the camera's position
    * and scale until Camera.on() is called
    *
    * @method off
    */
    this.off = function() {
      if(this.active)
      {
        cameraPop.call(pInst);
        this.active = false;
      }
    };
  } //end camera class
  
  defineLazyP5Property('Camera', boundConstructorFactory(Camera));
  
  //called pre draw by default
  function cameraPush() {
    var pInst = this;
    var camera = pInst.camera;
  
    //awkward but necessary in order to have the camera at the center
    //of the canvas by default
    if(!camera.init && camera.position.x === 0 && camera.position.y === 0)
      {
      camera.position.x=pInst.width/2;
      camera.position.y=pInst.height/2;
      camera.init = true;
      }
  
    camera.mouseX = pInst.mouseX+camera.position.x-pInst.width/2;
    camera.mouseY = pInst.mouseY+camera.position.y-pInst.height/2;
  
    if(!camera.active)
    {
      camera.active = true;
      pInst.push();
      pInst.scale(camera.zoom);
      pInst.translate(-camera.position.x+pInst.width/2/camera.zoom, -camera.position.y+pInst.height/2/camera.zoom);
    }
  }
  
  //called postdraw by default
  function cameraPop() {
    var pInst = this;
  
    if(pInst.camera.active)
    {
      pInst.pop();
      pInst.camera.active = false;
    }
  }
  
  
  
  
  /**
     * In p5.play groups are collections of sprites with similar behavior.
     * For example a group may contain all the sprites in the background
     * or all the sprites that "kill" the player.
     *
     * Groups are "extended" arrays and inherit all their properties
     * e.g. group.length
     *
     * Since groups contain only references, a sprite can be in multiple
     * groups and deleting a group doesn't affect the sprites themselves.
     *
     * Sprite.remove() will also remove the sprite from all the groups
     * it belongs to.
     *
     * @class Group
     * @constructor
     */
  function Group() {
  
    //basically extending the array
    var array = [];
  
    /**
    * Gets the member at index i.
    *
    * @method get
    * @param {Number} i The index of the object to retrieve
    */
    array.get = function(i) {
      return array[i];
    };
  
    /**
    * Checks if the group contains a sprite.
    *
    * @method contains
    * @param {Sprite} sprite The sprite to search
    * @return {Number} Index or -1 if not found
    */
    array.contains = function(sprite) {
      return this.indexOf(sprite)>-1;
    };
  
    /**
     * Same as Group.contains
     * @method indexOf
     */
    array.indexOf = function(item) {
      for (var i = 0, len = array.length; i < len; ++i) {
        if (virtEquals(item, array[i])) {
          return i;
        }
      }
      return -1;
    };
  
    /**
    * Adds a sprite to the group.
    *
    * @method add
    * @param {Sprite} s The sprite to be added
    */
    array.add = function(s) {
      if(!(s instanceof Sprite)) {
        throw('Error: you can only add sprites to a group');
      }
  
      if (-1 === this.indexOf(s)) {
        array.push(s);
        s.groups.push(this);
      }
    };
  
    /**
     * Same as group.length
     * @method size
     */
    array.size = function() {
      return array.length;
    };
  
    /**
    * Removes all the sprites in the group
    * from the scene.
    *
    * @method removeSprites
    */
    array.removeSprites = function() {
      while (array.length > 0) {
        array[0].remove();
      }
    };
  
    /**
    * Removes all references to the group.
    * Does not remove the actual sprites.
    *
    * @method clear
    */
    array.clear = function() {
      array.length = 0;
    };
  
    /**
    * Removes a sprite from the group.
    * Does not remove the actual sprite, only the affiliation (reference).
    *
    * @method remove
    * @param {Sprite} item The sprite to be removed
    * @return {Boolean} True if sprite was found and removed
    */
    array.remove = function(item) {
      if(!(item instanceof Sprite)) {
        throw('Error: you can only remove sprites from a group');
      }
  
      var i, removed = false;
      for (i = array.length - 1; i >= 0; i--) {
        if (array[i] === item) {
          array.splice(i, 1);
          removed = true;
        }
      }
  
      if (removed) {
        for (i = item.groups.length - 1; i >= 0; i--) {
          if (item.groups[i] === this) {
            item.groups.splice(i, 1);
          }
        }
      }
  
      return removed;
    };
  
    /**
     * Returns a copy of the group as standard array.
     * @method toArray
     */
    array.toArray = function() {
      return array.slice(0);
    };
  
    /**
    * Returns the highest depth in a group
    *
    * @method maxDepth
    * @return {Number} The depth of the sprite drawn on the top
    */
    array.maxDepth = function() {
      if (array.length === 0) {
        return 0;
      }
  
      return array.reduce(function(maxDepth, sprite) {
        return Math.max(maxDepth, sprite.depth);
      }, -Infinity);
    };
  
    /**
    * Returns the lowest depth in a group
    *
    * @method minDepth
    * @return {Number} The depth of the sprite drawn on the bottom
    */
    array.minDepth = function() {
      if (array.length === 0) {
        return 99999;
      }
  
      return array.reduce(function(minDepth, sprite) {
        return Math.min(minDepth, sprite.depth);
      }, Infinity);
    };
  
    /**
    * Draws all the sprites in the group.
    *
    * @method draw
    */
    array.draw = function() {
  
      //sort by depth
      this.sort(function(a, b) {
        return a.depth - b.depth;
      });
  
      for(var i = 0; i<this.size(); i++)
      {
        this.get(i).display();
      }
    };
  
    //internal use
    function virtEquals(obj, other) {
      if (obj === null || other === null) {
        return (obj === null) && (other === null);
      }
      if (typeof (obj) === 'string') {
        return obj === other;
      }
      if (typeof(obj) !== 'object') {
        return obj === other;
      }
      if (obj.equals instanceof Function) {
        return obj.equals(other);
      }
      return obj === other;
    }
  
    /**
     * Collide each member of group against the target using the given collision
     * type.  Return true if any collision occurred.
     * Internal use
     *
     * @private
     * @method _groupCollide
     * @param {!string} type one of 'overlap', 'collide', 'displace', 'bounce' or 'bounceOff'
     * @param {Object} target Group or Sprite
     * @param {Function} [callback] on collision.
     * @return {boolean} True if any collision/overlap occurred
     */
    function _groupCollide(type, target, callback) {
      var didCollide = false;
      for(var i = 0; i<this.size(); i++)
        didCollide = this.get(i)._collideWith(type, target, callback) || didCollide;
      return didCollide;
    }
  
    /**
    * Checks if the the group is overlapping another group or sprite.
    * The check is performed using the colliders. If colliders are not set
    * they will be created automatically from the image/animation bounding box.
    *
    * A callback function can be specified to perform additional operations
    * when the overlap occurs.
    * The function will be called for each single sprite overlapping.
    * The parameter of the function are respectively the
    * member of the current group and the other sprite passed as parameter.
    *
    * @example
    *     group.overlap(otherSprite, explosion);
    *
    *     function explosion(spriteA, spriteB) {
    *       spriteA.remove();
    *       spriteB.score++;
    *     }
    *
    * @method overlap
    * @param {Object} target Group or Sprite to check against the current one
    * @param {Function} [callback] The function to be called if overlap is positive
    * @return {Boolean} True if overlapping
    */
    array.overlap = _groupCollide.bind(array, 'overlap');
  
    /**
     * Alias for <a href='#method-overlap'>overlap()</a>
     *
     * Returns whether or not this group will bounce or collide with another sprite
     * or group. Modifies the each sprite's touching property object.
     *
     * @method isTouching
     * @param {Object} target Group or Sprite to check against the current one
     * @return {Boolean} True if touching
     */
    array.isTouching = array.overlap;
  
    /**
    * Checks if the the group is overlapping another group or sprite.
    * If the overlap is positive the sprites will bounce with the target(s)
    * treated as immovable with a restitution coefficient of zero.
    *
    * The check is performed using the colliders. If colliders are not set
    * they will be created automatically from the image/animation bounding box.
    *
    * A callback function can be specified to perform additional operations
    * when the overlap occours.
    * The function will be called for each single sprite overlapping.
    * The parameter of the function are respectively the
    * member of the current group and the other sprite passed as parameter.
    *
    * @example
    *     group.collide(otherSprite, explosion);
    *
    *     function explosion(spriteA, spriteB) {
    *       spriteA.remove();
    *       spriteB.score++;
    *     }
    *
    * @method collide
    * @param {Object} target Group or Sprite to check against the current one
    * @param {Function} [callback] The function to be called if overlap is positive
    * @return {Boolean} True if overlapping
    */
    array.collide = _groupCollide.bind(array, 'collide');
  
    /**
    * Checks if the the group is overlapping another group or sprite.
    * If the overlap is positive the sprites in the group will displace
    * the colliding ones to the closest non-overlapping positions.
    *
    * The check is performed using the colliders. If colliders are not set
    * they will be created automatically from the image/animation bounding box.
    *
    * A callback function can be specified to perform additional operations
    * when the overlap occurs.
    * The function will be called for each single sprite overlapping.
    * The parameter of the function are respectively the
    * member of the current group and the other sprite passed as parameter.
    *
    * @example
    *     group.displace(otherSprite, explosion);
    *
    *     function explosion(spriteA, spriteB) {
    *       spriteA.remove();
    *       spriteB.score++;
    *     }
    *
    * @method displace
    * @param {Object} target Group or Sprite to check against the current one
    * @param {Function} [callback] The function to be called if overlap is positive
    * @return {Boolean} True if overlapping
    */
    array.displace = _groupCollide.bind(array, 'displace');
  
    /**
    * Checks if the the group is overlapping another group or sprite.
    * If the overlap is positive the sprites will bounce affecting each
    * other's trajectories depending on their .velocity, .mass and .restitution.
    *
    * The check is performed using the colliders. If colliders are not set
    * they will be created automatically from the image/animation bounding box.
    *
    * A callback function can be specified to perform additional operations
    * when the overlap occours.
    * The function will be called for each single sprite overlapping.
    * The parameter of the function are respectively the
    * member of the current group and the other sprite passed as parameter.
    *
    * @example
    *     group.bounce(otherSprite, explosion);
    *
    *     function explosion(spriteA, spriteB) {
    *       spriteA.remove();
    *       spriteB.score++;
    *     }
    *
    * @method bounce
    * @param {Object} target Group or Sprite to check against the current one
    * @param {Function} [callback] The function to be called if overlap is positive
    * @return {Boolean} True if overlapping
    */
    array.bounce = _groupCollide.bind(array, 'bounce');
  
    /**
    * Checks if the the group is overlapping another group or sprite.
    * If the overlap is positive the sprites will bounce with the target(s)
    * treated as immovable.
    *
    * The check is performed using the colliders. If colliders are not set
    * they will be created automatically from the image/animation bounding box.
    *
    * A callback function can be specified to perform additional operations
    * when the overlap occours.
    * The function will be called for each single sprite overlapping.
    * The parameter of the function are respectively the
    * member of the current group and the other sprite passed as parameter.
    *
    * @example
    *     group.bounceOff(otherSprite, explosion);
    *
    *     function explosion(spriteA, spriteB) {
    *       spriteA.remove();
    *       spriteB.score++;
    *     }
    *
    * @method bounceOff
    * @param {Object} target Group or Sprite to check against the current one
    * @param {Function} [callback] The function to be called if overlap is positive
    * @return {Boolean} True if overlapping
    */
    array.bounceOff = _groupCollide.bind(array, 'bounceOff');
  
    array.setPropertyEach = function(propName, value) {
      for (var i = 0; i < this.length; i++) {
        this[i][propName] = value;
      }
    };
  
    array.callMethodEach = function(methodName) {
      // Copy all arguments after the first parameter into methodArgs:
      var methodArgs = Array.prototype.slice.call(arguments, 1);
      // Use a copy of the array in case the method modifies the group
      var elements = [].concat(this);
      for (var i = 0; i < elements.length; i++) {
        elements[i][methodName].apply(elements[i], methodArgs);
      }
    };
  
    array.setDepthEach = array.setPropertyEach.bind(array, 'depth');
    array.setLifetimeEach = array.setPropertyEach.bind(array, 'lifetime');
    array.setRotateToDirectionEach = array.setPropertyEach.bind(array, 'rotateToDirection');
    array.setRotationEach = array.setPropertyEach.bind(array, 'rotation');
    array.setRotationSpeedEach = array.setPropertyEach.bind(array, 'rotationSpeed');
    array.setScaleEach = array.setPropertyEach.bind(array, 'scale');
    array.setColorEach = array.setPropertyEach.bind(array, 'shapeColor');
    array.setTintEach = array.setPropertyEach.bind(array, 'tint');
    array.setVisibleEach = array.setPropertyEach.bind(array, 'visible');
    array.setVelocityXEach = array.setPropertyEach.bind(array, 'velocityX');
    array.setVelocityYEach = array.setPropertyEach.bind(array, 'velocityY');
    array.setHeightEach = array.setPropertyEach.bind(array, 'height');
    array.setWidthEach = array.setPropertyEach.bind(array, 'width');
  
    array.destroyEach = array.callMethodEach.bind(array, 'destroy');
    array.pointToEach = array.callMethodEach.bind(array, 'pointTo');
    array.setAnimationEach = array.callMethodEach.bind(array, 'setAnimation');
    array.setColliderEach = array.callMethodEach.bind(array, 'setCollider');
    array.setSpeedAndDirectionEach = array.callMethodEach.bind(array, 'setSpeedAndDirection');
    array.setVelocityEach = array.callMethodEach.bind(array, 'setVelocity');
    array.setMirrorXEach = array.callMethodEach.bind(array, 'mirrorX');
    array.setMirrorYEach = array.callMethodEach.bind(array, 'mirrorY');
  
    return array;
  }
  
  p5.prototype.Group = Group;
  
  /**
   * Creates four edge sprites and adds them to a group. Each edge is just outside
   * of the canvas and has a thickness of 100. After calling this function,
   * the following properties are exposed and populated with sprites:
   * leftEdge, rightEdge, topEdge, bottomEdge
   *
   * The 'edges' property is populated with a group containing those four sprites.
   *
   * If this edge sprites have already been created, the function returns the
   * existing edges group immediately.
   *
   * @method createEdgeSprites
   * @return {Group} The edges group
   */
  p5.prototype.createEdgeSprites = function() {
    if (this.edges) {
      return this.edges;
    }
  
    var edgeThickness = 100;
  
    var width = this._curElement.elt.offsetWidth;
    var height = this._curElement.elt.offsetHeight;
  
    this.leftEdge = this.createSprite(-edgeThickness / 2, height / 2, edgeThickness, height);
    this.rightEdge = this.createSprite(width + (edgeThickness / 2), height / 2, edgeThickness, height);
    this.topEdge = this.createSprite(width / 2, -edgeThickness / 2, width, edgeThickness);
    this.bottomEdge = this.createSprite(width / 2, height + (edgeThickness / 2), width, edgeThickness);
  
    this.edges = this.createGroup();
    this.edges.add(this.leftEdge);
    this.edges.add(this.rightEdge);
    this.edges.add(this.topEdge);
    this.edges.add(this.bottomEdge);
  
    return this.edges;
  };
  
  /**
   * An Animation object contains a series of images (p5.Image) that
   * can be displayed sequentially.
   *
   * All files must be png images. You must include the directory from the sketch root,
   * and the extension .png
   *
   * A sprite can have multiple labeled animations, see Sprite.addAnimation
   * and Sprite.changeAnimation, however an animation can be used independently.
   *
   * An animation can be created either by passing a series of file names,
   * no matter how many or by passing the first and the last file name
   * of a numbered sequence.
   * p5.play will try to detect the sequence pattern.
   *
   * For example if the given filenames are
   * "data/file0001.png" and "data/file0005.png" the images
   * "data/file0003.png" and "data/file0004.png" will be loaded as well.
   *
   * @example
   *     var sequenceAnimation;
   *     var glitch;
   *
   *     function preload() {
   *       sequenceAnimation = loadAnimation("data/walking0001.png", "data/walking0005.png");
   *       glitch = loadAnimation("data/dog.png", "data/horse.png", "data/cat.png", "data/snake.png");
   *     }
   *
   *     function setup() {
   *       createCanvas(800, 600);
   *     }
   *
   *     function draw() {
   *       background(0);
   *       animation(sequenceAnimation, 100, 100);
   *       animation(glitch, 200, 100);
   *     }
   *
   * @class Animation
   * @constructor
   * @param {String} fileName1 First file in a sequence OR first image file
   * @param {String} fileName2 Last file in a sequence OR second image file
   * @param {String} [...fileNameN] Any number of image files after the first two
   */
  function Animation(pInst) {
    var frameArguments = Array.prototype.slice.call(arguments, 1);
    var i;
  
    var CENTER = p5.prototype.CENTER;
  
    /**
    * Array of frames (p5.Image)
    *
    * @property images
    * @type {Array}
    */
    this.images = [];
  
    var frame = 0;
    var cycles = 0;
    var targetFrame = -1;
  
    this.offX = 0;
    this.offY = 0;
  
    /**
    * Delay between frames in number of draw cycles.
    * If set to 4 the framerate of the anymation would be the
    * sketch framerate divided by 4 (60fps = 15fps)
    *
    * @property frameDelay
    * @type {Number}
    * @default 2
    */
    this.frameDelay = 4;
  
    /**
    * True if the animation is currently playing.
    *
    * @property playing
    * @type {Boolean}
    * @default true
    */
    this.playing = true;
  
    /**
    * Animation visibility.
    *
    * @property visible
    * @type {Boolean}
    * @default true
    */
    this.visible = true;
  
    /**
    * If set to false the animation will stop after reaching the last frame
    *
    * @property looping
    * @type {Boolean}
    * @default true
    */
    this.looping = true;
  
    /**
    * True if frame changed during the last draw cycle
    *
    * @property frameChanged
    * @type {Boolean}
    */
    this.frameChanged = false;
  
    //is the collider defined manually or defined
    //by the current frame size
    this.imageCollider = false;
  
  
    //sequence mode
    if(frameArguments.length === 2 && typeof frameArguments[0] === 'string' && typeof frameArguments[1] === 'string')
    {
      var from = frameArguments[0];
      var to = frameArguments[1];
  
      //print("sequence mode "+from+" -> "+to);
  
      //make sure the extensions are fine
      var ext1 = from.substring(from.length-4, from.length);
      if(ext1 !== '.png')
      {
        pInst.print('Animation error: you need to use .png files (filename '+from+')');
        from = -1;
      }
  
      var ext2 = to.substring(to.length-4, to.length);
      if(ext2 !== '.png')
      {
        pInst.print('Animation error: you need to use .png files (filename '+to+')');
        to = -1;
      }
  
      //extensions are fine
      if(from !== -1 && to !== -1)
      {
        var digits1 = 0;
        var digits2 = 0;
  
        //skip extension work backwards to find the numbers
        for (i = from.length-5; i >= 0; i--) {
          if(from.charAt(i) >= '0' && from.charAt(i) <= '9')
            digits1++;
        }
  
        for (i = to.length-5; i >= 0; i--) {
          if(to.charAt(i) >= '0' && to.charAt(i) <= '9')
            digits2++;
        }
  
        var prefix1 = from.substring(0, from.length-(4+digits1));
        var prefix2 = to.substring(0, to.length-(4+digits2) );
  
        // Our numbers likely have leading zeroes, which means that some
        // browsers (e.g., PhantomJS) will interpret them as base 8 (octal)
        // instead of decimal. To fix this, we'll explicity tell parseInt to
        // use a base of 10 (decimal). For more details on this issue, see
        // http://stackoverflow.com/a/8763427/2422398.
        var number1 = parseInt(from.substring(from.length-(4+digits1), from.length-4), 10);
        var number2 = parseInt(to.substring(to.length-(4+digits2), to.length-4), 10);
  
        //swap if inverted
        if(number2<number1)
        {
          var t = number2;
          number2 = number1;
          number1 = t;
        }
  
        //two different frames
        if(prefix1 !== prefix2 )
        {
          //print("2 separate images");
          this.images.push(pInst.loadImage(from));
          this.images.push(pInst.loadImage(to));
        }
        //same digits: case img0001, img0002
        else
        {
          var fileName;
          if(digits1 === digits2)
          {
  
            //load all images
            for (i = number1; i <= number2; i++) {
              // Use nf() to number format 'i' into four digits
              fileName = prefix1 + pInst.nf(i, digits1) + '.png';
              this.images.push(pInst.loadImage(fileName));
  
            }
  
          }
          else //case: case img1, img2
          {
            //print("from "+prefix1+" "+number1 +" to "+number2);
            for (i = number1; i <= number2; i++) {
              // Use nf() to number format 'i' into four digits
              fileName = prefix1 + i + '.png';
              this.images.push(pInst.loadImage(fileName));
  
            }
  
          }
        }
  
      }//end no ext error
  
    }//end sequence mode
    // Sprite sheet mode
    else if (frameArguments.length === 1 && (frameArguments[0] instanceof SpriteSheet))
    {
      this.spriteSheet = frameArguments[0];
      this.images = this.spriteSheet.frames.map( function(f) {
        if (f.spriteSourceSize && f.sourceSize) {
          return Object.assign(f.frame, {
            width: f.frame.w,
            height: f.frame.h,
            sourceX: f.spriteSourceSize.x,
            sourceY: f.spriteSourceSize.y,
            sourceW: f.sourceSize.w,
            sourceH: f.sourceSize.h,
          });
        }
        return f.frame;
      });
    }
    else if(frameArguments.length !== 0)//arbitrary list of images
    {
      //print("Animation arbitrary mode");
      for (i = 0; i < frameArguments.length; i++) {
        //print("loading "+fileNames[i]);
        if(frameArguments[i] instanceof p5.Image)
          this.images.push(frameArguments[i]);
        else
          this.images.push(pInst.loadImage(frameArguments[i]));
      }
    }
  
    /**
    * Objects are passed by reference so to have different sprites
    * using the same animation you need to clone it.
    *
    * @method clone
    * @return {Animation} A clone of the current animation
    */
    this.clone = function() {
      var myClone = new Animation(pInst); //empty
      myClone.images = [];
  
      if (this.spriteSheet) {
        myClone.spriteSheet = this.spriteSheet.clone();
      }
      myClone.images = this.images.slice();
  
      myClone.offX = this.offX;
      myClone.offY = this.offY;
      myClone.frameDelay = this.frameDelay;
      myClone.playing = this.playing;
      myClone.looping = this.looping;
  
      return myClone;
    };
  
    /**
     * Draws the animation at coordinate x and y.
     * Updates the frames automatically.
     *
     * @method draw
     * @param {Number} x x coordinate
     * @param {Number} y y coordinate
     * @param {Number} [r=0] rotation
     */
    this.draw = function(x, y, r) {
      this.xpos = x;
      this.ypos = y;
      this.rotation = r || 0;
  
      if (this.visible)
      {
  
        //only connection with the sprite class
        //if animation is used independently draw and update are the sam
        if(!this.isSpriteAnimation)
          this.update();
  
        //this.currentImageMode = g.imageMode;
        pInst.push();
        pInst.imageMode(CENTER);
  
        var xTranslate = this.xpos;
        var yTranslate = this.ypos;
        var image = this.images[frame];
        var frame_info = this.spriteSheet && image;
  
        // Adjust translation if we're dealing with a texture packed spritesheet
        // (with sourceW, sourceH, sourceX, sourceY props on our images array)
        if (frame_info) {
          var missingX = (frame_info.sourceW || frame_info.width) - frame_info.width;
          var missingY = (frame_info.sourceH || frame_info.height) - frame_info.height;
          // If the count of missing (transparent) pixels is not equally balanced on
          // the left vs. right or top vs. bottom, we adjust the translation:
          xTranslate += ((frame_info.sourceX || 0) - missingX / 2);
          yTranslate += ((frame_info.sourceY || 0) - missingY / 2);
        }
  
        pInst.translate(xTranslate, yTranslate);
        if (pInst._angleMode === pInst.RADIANS) {
          pInst.rotate(radians(this.rotation));
        } else {
          pInst.rotate(this.rotation);
        }
  
        if (frame_info) {
          if (this.spriteSheet.image instanceof Image) {
            pInst.imageElement(this.spriteSheet.image,
              frame_info.x, frame_info.y,
              frame_info.width, frame_info.height,
              this.offX, this.offY,
              frame_info.width, frame_info.height);
          } else {
            pInst.image(this.spriteSheet.image,
              frame_info.x, frame_info.y,
              frame_info.width, frame_info.height,
              this.offX, this.offY,
              frame_info.width, frame_info.height);
            }
        } else if (image) {
          if (image instanceof Image) {
            pInst.imageElement(image, this.offX, this.offY);
          } else {
            pInst.image(image, this.offX, this.offY);
          }
        } else {
          pInst.print('Warning undefined frame '+frame);
          //this.isActive = false;
        }
  
        pInst.pop();
      }
    };
  
    //called by draw
    this.update = function() {
      cycles++;
      var previousFrame = frame;
      this.frameChanged = false;
  
  
      //go to frame
      if(this.images.length === 1)
      {
        this.playing = false;
        frame = 0;
      }
  
      if ( this.playing && cycles%this.frameDelay === 0)
      {
        //going to target frame up
        if(targetFrame>frame && targetFrame !== -1)
        {
          frame++;
        }
        //going to taget frame down
        else if(targetFrame<frame && targetFrame !== -1)
        {
          frame--;
        }
        else if(targetFrame === frame && targetFrame !== -1)
        {
          this.playing=false;
        }
        else if (this.looping) //advance frame
        {
          //if next frame is too high
          if (frame>=this.images.length-1)
            frame = 0;
          else
            frame++;
        } else
        {
          //if next frame is too high
          if (frame<this.images.length-1)
            frame++;
          else
            this.playing = false;
        }
      }
  
      if(previousFrame !== frame)
        this.frameChanged = true;
  
    };//end update
  
    /**
    * Plays the animation.
    *
    * @method play
    */
    this.play = function() {
      this.playing = true;
      targetFrame = -1;
    };
  
    /**
    * Stops the animation.
    *
    * @method stop
    */
    this.stop = function(){
      this.playing = false;
    };
  
    /**
    * Rewinds the animation to the first frame.
    *
    * @method rewind
    */
    this.rewind = function() {
      frame = 0;
    };
  
    /**
    * Changes the current frame.
    *
    * @method changeFrame
    * @param {Number} frame Frame number (starts from 0).
    */
    this.changeFrame = function(f) {
      if (f<this.images.length)
        frame = f;
      else
        frame = this.images.length - 1;
  
      targetFrame = -1;
      //this.playing = false;
    };
  
    /**
     * Goes to the next frame and stops.
     *
     * @method nextFrame
     */
    this.nextFrame = function() {
  
      if (frame<this.images.length-1)
        frame = frame+1;
      else if(this.looping)
        frame = 0;
  
      targetFrame = -1;
      this.playing = false;
    };
  
    /**
     * Goes to the previous frame and stops.
     *
     * @method previousFrame
     */
    this.previousFrame = function() {
  
      if (frame>0)
        frame = frame-1;
      else if(this.looping)
        frame = this.images.length-1;
  
      targetFrame = -1;
      this.playing = false;
    };
  
    /**
    * Plays the animation forward or backward toward a target frame.
    *
    * @method goToFrame
    * @param {Number} toFrame Frame number destination (starts from 0)
    */
    this.goToFrame = function(toFrame) {
      if(toFrame < 0 || toFrame >= this.images.length) {
        return;
      }
  
      // targetFrame gets used by the update() method to decide what frame to
      // select next.  When it's not being used it gets set to -1.
      targetFrame = toFrame;
  
      if(targetFrame !== frame) {
        this.playing = true;
      }
    };
  
    /**
    * Returns the current frame number.
    *
    * @method getFrame
    * @return {Number} Current frame (starts from 0)
    */
    this.getFrame = function() {
      return frame;
    };
  
    /**
    * Returns the last frame number.
    *
    * @method getLastFrame
    * @return {Number} Last frame number (starts from 0)
    */
    this.getLastFrame = function() {
      return this.images.length-1;
    };
  
    /**
    * Returns the current frame image as p5.Image.
    *
    * @method getFrameImage
    * @return {p5.Image} Current frame image
    */
    this.getFrameImage = function() {
      return this.images[frame];
    };
  
    /**
    * Returns the frame image at the specified frame number.
    *
    * @method getImageAt
    * @param {Number} frame Frame number
    * @return {p5.Image} Frame image
    */
    this.getImageAt = function(f) {
      return this.images[f];
    };
  
    /**
    * Returns the current frame width in pixels.
    * If there is no image loaded, returns 1.
    *
    * @method getWidth
    * @return {Number} Frame width
    */
    this.getWidth = function() {
      if (this.images[frame]) {
        return this.images[frame].sourceW || this.images[frame].width;
      } else {
        return 1;
      }
    };
  
    /**
    * Returns the current frame height in pixels.
    * If there is no image loaded, returns 1.
    *
    * @method getHeight
    * @return {Number} Frame height
    */
    this.getHeight = function() {
      if (this.images[frame]) {
        return this.images[frame].sourceH || this.images[frame].height;
      } else {
        return 1;
      }
    };
  
  }
  
  defineLazyP5Property('Animation', boundConstructorFactory(Animation));
  
  /**
   * Represents a sprite sheet and all it's frames.  To be used with Animation,
   * or static drawing single frames.
   *
   *  There are two different ways to load a SpriteSheet
   *
   * 1. Given width, height that will be used for every frame and the
   *    number of frames to cycle through. The sprite sheet must have a
   *    uniform grid with consistent rows and columns.
   *
   * 2. Given an array of frame objects that define the position and
   *    dimensions of each frame.  This is Flexible because you can use
   *    sprite sheets that don't have uniform rows and columns.
   *
   * @example
   *     // Method 1 - Using width, height for each frame and number of frames
   *     explode_sprite_sheet = loadSpriteSheet('assets/explode_sprite_sheet.png', 171, 158, 11);
   *
   *     // Method 2 - Using an array of objects that define each frame
   *     var player_frames = loadJSON('assets/tiles.json');
   *     player_sprite_sheet = loadSpriteSheet('assets/player_spritesheet.png', player_frames);
   *
   * @class SpriteSheet
   * @constructor
   * @param image String image path or p5.Image object
   */
  function SpriteSheet(pInst) {
    var spriteSheetArgs = Array.prototype.slice.call(arguments, 1);
  
    this.image = null;
    this.frames = [];
    this.frame_width = 0;
    this.frame_height = 0;
    this.num_frames = 0;
  
    /**
     * Generate the frames data for this sprite sheet baesd on user params
     * @private
     * @method _generateSheetFrames
     */
    this._generateSheetFrames = function() {
      var sX = 0, sY = 0;
      for (var i = 0; i < this.num_frames; i++) {
        this.frames.push(
          {
            'name': i,
            'frame': {
              'x': sX,
              'y': sY,
              'width': this.frame_width,
              'height': this.frame_height
            }
          });
        sX += this.frame_width;
        if (sX >= this.image.width) {
          sX = 0;
          sY += this.frame_height;
          if (sY >= this.image.height) {
            sY = 0;
          }
        }
      }
    };
  
    var shortArgs = spriteSheetArgs.length === 2 || spriteSheetArgs.length === 3;
    var longArgs = spriteSheetArgs.length === 4 || spriteSheetArgs.length === 5;
  
    if (shortArgs && Array.isArray(spriteSheetArgs[1])) {
      this.frames = spriteSheetArgs[1];
      this.num_frames = this.frames.length;
    } else if (longArgs &&
      (typeof spriteSheetArgs[1] === 'number') &&
      (typeof spriteSheetArgs[2] === 'number') &&
      (typeof spriteSheetArgs[3] === 'number')) {
      this.frame_width = spriteSheetArgs[1];
      this.frame_height = spriteSheetArgs[2];
      this.num_frames = spriteSheetArgs[3];
    }
  
    if(spriteSheetArgs[0] instanceof p5.Image || spriteSheetArgs[0] instanceof Image) {
      this.image = spriteSheetArgs[0];
      if (longArgs) {
        this._generateSheetFrames();
      }
    } else {
      // When the final argument is present (either the 3rd or the 5th), it indicates
      // whether we should load the URL as an Image element (as opposed to the default
      // behavior, which is to load it as a p5.Image). If that argument is a function,
      // it will be called back once the load succeeds or fails. On success, the Image
      // will be supplied as the only parameter. On failure, null will be supplied.
      var callback;
      if (shortArgs) {
        if (spriteSheetArgs[2]) {
          if (typeof spriteSheetArgs[2] === 'function') {
            callback = spriteSheetArgs[2];
          }
          this.image = pInst.loadImageElement(
            spriteSheetArgs[0],
            function(img) { if (callback) return callback(img); },
            function() { if (callback) return callback(null); }
          );
        } else {
          this.image = pInst.loadImage(spriteSheetArgs[0]);
        }
      } else if (longArgs) {
        var generateSheetFrames = this._generateSheetFrames.bind(this);
        if (spriteSheetArgs[4]) {
          if (typeof spriteSheetArgs[4] === 'function') {
            callback = spriteSheetArgs[4];
          }
          this.image = pInst.loadImageElement(
            spriteSheetArgs[0],
            function(img) {
              generateSheetFrames(img);
              if (callback) return callback(img);
            },
            function() { if (callback) return callback(null); }
          );
        } else {
          this.image = pInst.loadImage(spriteSheetArgs[0], generateSheetFrames);
        }
      }
    }
  
    /**
     * Draws a specific frame to the canvas.
     * @param frame_name  Can either be a string name, or a numeric index.
     * @param x   x position to draw the frame at
     * @param y   y position to draw the frame at
     * @param [width]   optional width to draw the frame
     * @param [height]  optional height to draw the frame
     * @method drawFrame
     */
    this.drawFrame = function(frame_name, x, y, width, height) {
      var frameToDraw;
      if (typeof frame_name === 'number') {
        frameToDraw = this.frames[frame_name];
      } else {
        for (var i = 0; i < this.frames.length; i++) {
          if (this.frames[i].name === frame_name) {
            frameToDraw = this.frames[i];
            break;
          }
        }
      }
      var frameWidth = frameToDraw.frame.width || frameToDraw.frame.w;
      var frameHeight = frameToDraw.frame.height || frameToDraw.frame.h;
      var dWidth = width || frameWidth;
      var dHeight = height || frameHeight;
  
      // Adjust how we draw if we're dealing with a texture packed spritesheet
      // (in particular, we treat supplied width and height params as an intention
      //  to scale versus the sourceSize [before packing])
      if (frameToDraw.spriteSourceSize && frameToDraw.sourceSize) {
        var frameSizeScaleX = frameWidth / frameToDraw.sourceSize.w;
        var frameSizeScaleY = frameHeight / frameToDraw.sourceSize.h;
        if (width) {
          x += (frameToDraw.spriteSourceSize.x * dWidth / frameToDraw.sourceSize.w);
          dWidth = width * frameSizeScaleX;
        } else {
          x += frameToDraw.spriteSourceSize.x;
        }
        if (height) {
          y += (frameToDraw.spriteSourceSize.y * dHeight / frameToDraw.sourceSize.h);
          dHeight = height * frameSizeScaleY;
        } else {
          y += frameToDraw.spriteSourceSize.y;
        }
      }
      if (this.image instanceof Image) {
        pInst.imageElement(this.image, frameToDraw.frame.x, frameToDraw.frame.y,
          frameToDraw.frame.width, frameToDraw.frame.height, x, y, dWidth, dHeight);
      } else {
        pInst.image(this.image, frameToDraw.frame.x, frameToDraw.frame.y,
          frameToDraw.frame.width, frameToDraw.frame.height, x, y, dWidth, dHeight);
      }
    };
  
    /**
     * Objects are passed by reference so to have different sprites
     * using the same animation you need to clone it.
     *
     * @method clone
     * @return {SpriteSheet} A clone of the current SpriteSheet
     */
    this.clone = function() {
      var myClone = new SpriteSheet(pInst); //empty
  
      // Deep clone the frames by value not reference
      for(var i = 0; i < this.frames.length; i++) {
        var frame = this.frames[i].frame;
        var cloneFrame = {
          'name':frame.name,
          'frame': {
            'x':frame.x,
            'y':frame.y,
            'width':frame.width,
            'height':frame.height
          }
        };
        myClone.frames.push(cloneFrame);
      }
  
      // clone other fields
      myClone.image = this.image;
      myClone.frame_width = this.frame_width;
      myClone.frame_height = this.frame_height;
      myClone.num_frames = this.num_frames;
  
      return myClone;
    };
  }
  
  defineLazyP5Property('SpriteSheet', boundConstructorFactory(SpriteSheet));
  
  //general constructor to be able to feed arguments as array
  function construct(constructor, args) {
    function F() {
      return constructor.apply(this, args);
    }
    F.prototype = constructor.prototype;
    return new F();
  }
  
  
  
  
  
  /*
   * Javascript Quadtree
   * based on
   * https://github.com/timohausmann/quadtree-js/
   * Copyright © 2012 Timo Hausmann
  */
  
  function Quadtree( bounds, max_objects, max_levels, level ) {
  
    this.active = true;
    this.max_objects	= max_objects || 10;
    this.max_levels		= max_levels || 4;
  
    this.level 			= level || 0;
    this.bounds 		= bounds;
  
    this.objects 		= [];
    this.object_refs	= [];
    this.nodes 			= [];
  }
  
  Quadtree.prototype.updateBounds = function() {
  
    //find maximum area
    var objects = this.getAll();
    var x = 10000;
    var y = 10000;
    var w = -10000;
    var h = -10000;
  
    for( var i=0; i < objects.length; i++ )
      {
        if(objects[i].position.x < x)
          x = objects[i].position.x;
        if(objects[i].position.y < y)
          y = objects[i].position.y;
        if(objects[i].position.x > w)
          w = objects[i].position.x;
        if(objects[i].position.y > h)
          h = objects[i].position.y;
      }
  
  
    this.bounds = {
      x:x,
      y:y,
      width:w,
      height:h
    };
    //print(this.bounds);
  };
  
  /*
  	 * Split the node into 4 subnodes
  	 */
  Quadtree.prototype.split = function() {
  
    var nextLevel	= this.level + 1,
        subWidth	= Math.round( this.bounds.width / 2 ),
        subHeight 	= Math.round( this.bounds.height / 2 ),
        x 			= Math.round( this.bounds.x ),
        y 			= Math.round( this.bounds.y );
  
    //top right node
    this.nodes[0] = new Quadtree({
      x	: x + subWidth,
      y	: y,
      width	: subWidth,
      height	: subHeight
    }, this.max_objects, this.max_levels, nextLevel);
  
    //top left node
    this.nodes[1] = new Quadtree({
      x	: x,
      y	: y,
      width	: subWidth,
      height	: subHeight
    }, this.max_objects, this.max_levels, nextLevel);
  
    //bottom left node
    this.nodes[2] = new Quadtree({
      x	: x,
      y	: y + subHeight,
      width	: subWidth,
      height	: subHeight
    }, this.max_objects, this.max_levels, nextLevel);
  
    //bottom right node
    this.nodes[3] = new Quadtree({
      x	: x + subWidth,
      y	: y + subHeight,
      width	: subWidth,
      height	: subHeight
    }, this.max_objects, this.max_levels, nextLevel);
  };
  
  
  /*
  	 * Determine the quadtrant for an area in this node
  	 */
  Quadtree.prototype.getIndex = function( pRect ) {
    if(!pRect.collider)
      return -1;
    else
    {
      var colliderBounds = pRect.collider.getBoundingBox();
      var index 				= -1,
          verticalMidpoint 	= this.bounds.x + (this.bounds.width / 2),
          horizontalMidpoint 	= this.bounds.y + (this.bounds.height / 2),
  
          //pRect can completely fit within the top quadrants
          topQuadrant = (colliderBounds.top < horizontalMidpoint && colliderBounds.bottom < horizontalMidpoint),
  
          //pRect can completely fit within the bottom quadrants
          bottomQuadrant = (colliderBounds.top > horizontalMidpoint);
  
      //pRect can completely fit within the left quadrants
      if (colliderBounds.left < verticalMidpoint && colliderBounds.right < verticalMidpoint ) {
        if( topQuadrant ) {
          index = 1;
        } else if( bottomQuadrant ) {
          index = 2;
        }
  
        //pRect can completely fit within the right quadrants
      } else if( colliderBounds.left > verticalMidpoint ) {
        if( topQuadrant ) {
          index = 0;
        } else if( bottomQuadrant ) {
          index = 3;
        }
      }
  
      return index;
    }
  };
  
  
  /*
  	 * Insert an object into the node. If the node
  	 * exceeds the capacity, it will split and add all
  	 * objects to their corresponding subnodes.
  	 */
  Quadtree.prototype.insert = function( obj ) {
    //avoid double insertion
    if(this.objects.indexOf(obj) === -1)
    {
  
      var i = 0,
          index;
  
      //if we have subnodes ...
      if( typeof this.nodes[0] !== 'undefined' ) {
        index = this.getIndex( obj );
  
        if( index !== -1 ) {
          this.nodes[index].insert( obj );
          return;
        }
      }
  
      this.objects.push( obj );
  
      if( this.objects.length > this.max_objects && this.level < this.max_levels ) {
  
        //split if we don't already have subnodes
        if( typeof this.nodes[0] === 'undefined' ) {
          this.split();
        }
  
        //add all objects to there corresponding subnodes
        while( i < this.objects.length ) {
  
          index = this.getIndex( this.objects[i] );
  
          if( index !== -1 ) {
            this.nodes[index].insert( this.objects.splice(i, 1)[0] );
          } else {
            i = i + 1;
          }
        }
      }
    }
  };
  
  
  /*
  	 * Return all objects that could collide with a given area
  	 */
  Quadtree.prototype.retrieve = function( pRect ) {
  
  
    var index = this.getIndex( pRect ),
        returnObjects = this.objects;
  
    //if we have subnodes ...
    if( typeof this.nodes[0] !== 'undefined' ) {
  
      //if pRect fits into a subnode ..
      if( index !== -1 ) {
        returnObjects = returnObjects.concat( this.nodes[index].retrieve( pRect ) );
  
        //if pRect does not fit into a subnode, check it against all subnodes
      } else {
        for( var i=0; i < this.nodes.length; i=i+1 ) {
          returnObjects = returnObjects.concat( this.nodes[i].retrieve( pRect ) );
        }
      }
    }
  
    return returnObjects;
  };
  
  Quadtree.prototype.retrieveFromGroup = function( pRect, group ) {
  
    var results = [];
    var candidates = this.retrieve(pRect);
  
    for(var i=0; i<candidates.length; i++)
      if(group.contains(candidates[i]))
      results.push(candidates[i]);
  
    return results;
  };
  
  /*
  	 * Get all objects stored in the quadtree
  	 */
  Quadtree.prototype.getAll = function() {
  
    var objects = this.objects;
  
    for( var i=0; i < this.nodes.length; i=i+1 ) {
      objects = objects.concat( this.nodes[i].getAll() );
    }
  
    return objects;
  };
  
  
  /*
  	 * Get the node in which a certain object is stored
  	 */
  Quadtree.prototype.getObjectNode = function( obj ) {
  
    var index;
  
    //if there are no subnodes, object must be here
    if( !this.nodes.length ) {
  
      return this;
  
    } else {
  
      index = this.getIndex( obj );
  
      //if the object does not fit into a subnode, it must be here
      if( index === -1 ) {
  
        return this;
  
        //if it fits into a subnode, continue deeper search there
      } else {
        var node = this.nodes[index].getObjectNode( obj );
        if( node ) return node;
      }
    }
  
    return false;
  };
  
  
  /*
  	 * Removes a specific object from the quadtree
  	 * Does not delete empty subnodes. See cleanup-function
  	 */
  Quadtree.prototype.removeObject = function( obj ) {
  
    var node = this.getObjectNode( obj ),
        index = node.objects.indexOf( obj );
  
    if( index === -1 ) return false;
  
    node.objects.splice( index, 1);
  };
  
  
  /*
  	 * Clear the quadtree and delete all objects
  	 */
  Quadtree.prototype.clear = function() {
  
    this.objects = [];
  
    if( !this.nodes.length ) return;
  
    for( var i=0; i < this.nodes.length; i=i+1 ) {
  
      this.nodes[i].clear();
    }
  
    this.nodes = [];
  };
  
  
  /*
  	 * Clean up the quadtree
  	 * Like clear, but objects won't be deleted but re-inserted
  	 */
  Quadtree.prototype.cleanup = function() {
  
    var objects = this.getAll();
  
    this.clear();
  
    for( var i=0; i < objects.length; i++ ) {
      this.insert( objects[i] );
    }
  };
  
  
  
  function updateTree() {
    if(this.quadTree.active)
    {
      this.quadTree.updateBounds();
      this.quadTree.cleanup();
    }
  }
  
  //keyboard input
  p5.prototype.registerMethod('pre', p5.prototype.readPresses);
  
  //automatic sprite update
  p5.prototype.registerMethod('pre', p5.prototype.updateSprites);
  
  //quadtree update
  p5.prototype.registerMethod('post', updateTree);
  
  //camera push and pop
  p5.prototype.registerMethod('pre', cameraPush);
  p5.prototype.registerMethod('post', cameraPop);
  
  p5.prototype.registerPreloadMethod('loadImageElement', p5.prototype);
  
  //deltaTime
  //p5.prototype.registerMethod('pre', updateDelta);
  
  /**
   * Log a warning message to the host console, using native `console.warn`
   * if it is available but falling back on `console.log` if not.  If no
   * console is available, this method will fail silently.
   * @method _warn
   * @param {!string} message
   * @private
   */
  p5.prototype._warn = function(message) {
    var console = window.console;
  
    if(console)
    {
      if('function' === typeof console.warn)
      {
        console.warn(message);
      }
      else if('function' === typeof console.log)
      {
        console.log('Warning: ' + message);
      }
    }
  };
  
    /**
     * Collision Shape Base Class
     *
     * We have a set of collision shapes available that all conform to
     * a simple interface so that they can be checked against one another
     * using the Separating Axis Theorem.
     *
     * This base class implements all the required methods for a collision
     * shape and can be used as a collision point with no changes.
     * Other shapes should inherit from this and override most methods.
     *
     * @class p5.CollisionShape
     * @constructor
     * @param {p5.Vector} [center] (zero if omitted)
     * @param {number} [rotation] (zero if omitted)
     */
    p5.CollisionShape = function(center, rotation) {
      /**
       * Transform of this shape relative to its parent.  If there is no parent,
       * this is pretty much the world-space transform.
       * This should stay consistent with _offset, _rotation and _scale properties.
       * @property _localTransform
       * @type {p5.Transform2D}
       * @protected
       */
      this._localTransform = new p5.Transform2D();
      if (rotation) {
        this._localTransform.rotate(rotation);
      }
      if (center) {
        this._localTransform.translate(center);
      }
  
      /**
       * Transform of whatever parent object (probably a sprite) this shape is
       * associated with.  If this is a free-floating shape, the parent transform
       * will remain an identity matrix.
       * @property _parentTransform
       * @type {p5.Transform2D}
       * @protected
       */
      this._parentTransform = new p5.Transform2D();
  
      /**
       * The center of the collision shape in world-space.
       * @property _center
       * @private
       * @type {p5.Vector}
       */
      this._center = new p5.Vector();
  
      /**
       * The center of the collision shape in local-space; also, the offset of the
       * collision shape's center from its parent sprite's center.
       * @property _offset
       * @type {p5.Vector}
       * @private
       */
      this._offset = new p5.Vector();
  
      /**
       * Rotation in radians in local space (relative to parent).
       * Note that this will only be meaningful for shapes that can rotate,
       * i.e. Oriented Bounding Boxes
       * @property _rotation
       * @private
       * @type {number}
       */
      this._rotation = 0;
  
      /**
       * Scale X and Y in local space.  Note that this will only be meaningful
       * for shapes that have dimensions (e.g. not for point colliders)
       * @property _scale
       * @type {p5.Vector}
       * @private
       */
      this._scale = new p5.Vector(1, 1);
  
      /**
       * If true, when calling `updateFromSprite` this collider will adopt the
       * base dimensions of the sprite in addition to adopting its transform.
       * If false, only the transform (position/rotation/scale) will be adopted.
       * @property getsDimensionsFromSprite
       * @type {boolean}
       */
      this.getsDimensionsFromSprite = false;
  
      // Public getters/setters
      Object.defineProperties(this, {
  
        /**
         * The center of the collision shape in world-space.
         * Note: You can set this property with a value in world-space, but it will
         * actually modify the collision shape's local transform.
         * @property center
         * @type {p5.Vector}
         */
        'center': {
          enumerable: true,
          get: function() {
            return this._center.copy();
          }.bind(this),
          set: function(c) {
            this._localTransform
              .translate(p5.Vector.mult(this._center, -1))
              .translate(c);
            this._onTransformChanged();
          }.bind(this)
        },
  
        /**
         * The center of the collision shape in local-space - if this collider is
         * owned by a sprite, the offset of the collider center from the sprite center.
         * @property offset
         * @type {p5.Vector}
         */
        'offset': {
          enumerable: true,
          get: function() {
            return this._offset.copy();
          }.bind(this),
          set: function(o) {
            this._localTransform
              .translate(p5.Vector.mult(this._offset, -1))
              .translate(o);
            this._onTransformChanged();
          }.bind(this)
        },
  
        /**
         * The local-space rotation of the collider, in radians.
         * @property rotation
         * @type {number}
         */
        'rotation': {
          enumerable: true,
          get: function() {
            return this._rotation;
          }.bind(this),
          set: function(r) {
            this._localTransform
              .clear()
              .scale(this._scale)
              .rotate(r)
              .translate(this._offset);
            this._onTransformChanged();
          }.bind(this)
        },
  
        /**
         * The local-space scale of the collider
         * @property scale
         * @type {p5.Vector}
         */
        'scale': {
          enumerable: true,
          get: function() {
            return this._scale.copy();
          }.bind(this),
          set: function(s) {
            this._localTransform
              .clear()
              .scale(s)
              .rotate(this._rotation)
              .translate(this._offset);
            this._onTransformChanged();
          }.bind(this)
        }
      });
  
      this._onTransformChanged();
    };
  
    /**
     * Update this collider based on the properties of a parent Sprite.
     * Descendant classes should override this method to adopt the dimensions
     * of the sprite if `getsDimensionsFromSprite` is true.
     * @method updateFromSprite
     * @param {Sprite} sprite
     * @see p5.CollisionShape.prototype.getsDimensionsFromSprite
     */
    p5.CollisionShape.prototype.updateFromSprite = function(sprite) {
      this.setParentTransform(sprite);
    };
  
    /**
     * Update this collider's parent transform, which will in turn adjust its
     * position, rotation and scale in world-space and recompute cached values
     * if necessary.
     * If a Sprite is passed as the 'parent' then a new transform will be computed
     * from the sprite's position/rotation/scale and used.
     * @method setParentTransform
     * @param {p5.Transform2D|Sprite} parent
     */
    p5.CollisionShape.prototype.setParentTransform = function(parent) {
      if (parent instanceof Sprite) {
        this._parentTransform
          .clear()
          .scale(parent._getScaleX(), parent._getScaleY())
          .rotate(radians(parent.rotation))
          .translate(parent.position);
      } else if (parent instanceof p5.Transform2D) {
        this._parentTransform = parent.copy();
      } else {
        throw new TypeError('Bad argument to setParentTransform: ' + parent);
      }
      this._onTransformChanged();
    };
  
    /**
     * Recalculate cached properties, relevant vectors, etc. when at least one
     * of the shape's transforms changes.  The base CollisionShape (and PointCollider)
     * only need to recompute the shape's center, but other shapes may need to
     * override this method and do additional recomputation.
     * @method _onTransformChanged
     * @protected
     */
    p5.CollisionShape.prototype._onTransformChanged = function() {
      // Recompute internal properties from transforms
  
      // Rotation in local space
      this._rotation = this._localTransform.getRotation();
  
      // Scale in local space
      this._scale = this._localTransform.getScale();
  
      // Offset in local-space
      this._offset
        .set(0, 0)
        .transform(this._localTransform);
  
      // Center in world-space
      this._center
        .set(this._offset.x, this._offset.y)
        .transform(this._parentTransform);
    };
  
    /**
     * Compute the smallest movement needed to move this collision shape out of
     * another collision shape.  If the shapes are not overlapping, returns a
     * zero vector to indicate that no displacement is necessary.
     * @method collide
     * @param {p5.CollisionShape} other
     * @return {p5.Vector}
     */
    p5.CollisionShape.prototype.collide = function(other) {
      var displacee = this, displacer = other;
  
      // Compute a displacement vector using the Separating Axis Theorem
      // (Valid only for convex shapes)
      //
      // If a line (axis) exists on which the two shapes' orthogonal projections
      // do not overlap, then the shapes do not overlap.  If the shapes'
      // projections do overlap on all candidate axes, the axis that had the
      // smallest overlap gives us the smallest possible displacement.
      //
      // @see http://www.dyn4j.org/2010/01/sat/
      var smallestOverlap = Infinity;
      var smallestOverlapAxis = null;
  
      // We speed things up with an additional assumption that all collision
      // shapes are centrosymmetric: Circles, ellipses, and rectangles
      // are OK.  This lets us only compare the shapes' radii to the
      // distance between their centers, even for non-circular shapes.
      // Other convex shapes, (triangles, pentagons) will require more
      // complex use of their projections' positions on the axis.
      var deltaOfCenters = p5.Vector.sub(displacer.center, displacee.center);
  
      // It turns out we only need to check a few axes, defined by the shapes
      // being checked.  For a polygon, the normal of each face is a possible
      // separating axis.
      var candidateAxes = p5.CollisionShape._getCandidateAxesForShapes(displacee, displacer);
      var axis, deltaOfCentersOnAxis, distanceOfCentersOnAxis;
      for (var i = 0; i < candidateAxes.length; i++) {
        axis = candidateAxes[i];
  
        // If distance between the shape's centers as projected onto the
        // separating axis is larger than the combined radii of the shapes
        // projected onto the axis, the shapes do not overlap on this axis.
        deltaOfCentersOnAxis = p5.Vector.project(deltaOfCenters, axis);
        distanceOfCentersOnAxis = deltaOfCentersOnAxis.mag();
        var r1 = displacee._getRadiusOnAxis(axis);
        var r2 = displacer._getRadiusOnAxis(axis);
        var overlap = r1 + r2 - distanceOfCentersOnAxis;
        if (overlap <= 0) {
          // These shapes are separated along this axis.
          // Early-out, returning a zero-vector displacement.
          return new p5.Vector();
        } else if (overlap < smallestOverlap) {
          // This is the smallest overlap we've found so far - store some
          // information about it, which we can use to give the smallest
          // displacement when we're done.
          smallestOverlap = overlap;
          // Normally use the delta of centers, which gives us direction along
          // with an axis.  In the rare case that the centers exactly overlap,
          // just use the original axis
          if (deltaOfCentersOnAxis.x === 0 && deltaOfCentersOnAxis.y === 0) {
            smallestOverlapAxis = axis;
          } else {
            smallestOverlapAxis = deltaOfCentersOnAxis;
          }
        }
      }
  
      // If we make it here, we overlap on all possible axes and we
      // can compute the smallest vector that will displace this out of other.
      return smallestOverlapAxis.copy().setMag(-smallestOverlap);
    };
  
  
    /**
     * Check whether this shape overlaps another.
     * @method overlap
     * @param {p5.CollisionShape} other
     * @return {boolean}
     */
    p5.CollisionShape.prototype.overlap = function(other) {
      var displacement = this.collide(other);
      return displacement.x !== 0 || displacement.y !== 0;
    };
  
    /**
     * @method _getCanididateAxesForShapes
     * @private
     * @static
     * @param {p5.CollisionShape} shape1
     * @param {p5.CollisionShape} shape2
     * @return {Array.<p5.Vector>}
     */
    p5.CollisionShape._getCandidateAxesForShapes = function(shape1, shape2) {
      var axes = shape1._getCandidateAxes(shape2)
        .concat(shape2._getCandidateAxes(shape1))
        .map(function(axis) {
          if (axis.x === 0 && axis.y === 0) {
            return p5.CollisionShape.X_AXIS;
          }
          return axis;
        });
      return deduplicateParallelVectors(axes);
    };
  
    /*
     * Reduce an array of vectors to a set of unique axes (that is, no two vectors
     * in the array should be parallel).
     * @param {Array.<p5.Vector>} array
     * @return {Array}
     */
    function deduplicateParallelVectors(array) {
      return array.filter(function(item, itemPos) {
        return !array.some(function(other, otherPos) {
          return itemPos < otherPos && item.isParallel(other);
        });
      });
    }
  
    /**
     * Compute candidate separating axes relative to another object.
     * Override this method in subclasses to implement collision behavior.
     * @method _getCandidateAxes
     * @protected
     * @return {Array.<p5.Vector>}
     */
    p5.CollisionShape.prototype._getCandidateAxes = function() {
      return [];
    };
  
    /**
     * Get this shape's radius (half-width of its projection) along the given axis.
     * Override this method in subclasses to implement collision behavior.
     * @method _getRadiusOnAxis
     * @protected
     * @param {p5.Vector} axis
     * @return {number}
     */
    p5.CollisionShape.prototype._getRadiusOnAxis = function() {
      return 0;
    };
  
    /**
     * Get the shape's minimum radius on any axis for tunneling checks.
     * @method _getMinRadius
     * @protected
     * @param {p5.Vector} axis
     * @return {number}
     */
    p5.CollisionShape.prototype._getMinRadius = function() {
      return 0;
    };
  
    /**
     * @property X_AXIS
     * @type {p5.Vector}
     * @static
     * @final
     */
    p5.CollisionShape.X_AXIS = new p5.Vector(1, 0);
  
    /**
     * @property Y_AXIS
     * @type {p5.Vector}
     * @static
     * @final
     */
    p5.CollisionShape.Y_AXIS = new p5.Vector(0, 1);
  
    /**
     * @property WORLD_AXES
     * @type {Array.<p5.Vector>}
     * @static
     * @final
     */
    p5.CollisionShape.WORLD_AXES = [
      p5.CollisionShape.X_AXIS,
      p5.CollisionShape.Y_AXIS
    ];
  
    /**
     * Get world-space axis-aligned bounds information for this collision shape.
     * Used primarily for the quadtree.
     * @method getBoundingBox
     * @return {{top: number, bottom: number, left: number, right: number, width: number, height: number}}
     */
    p5.CollisionShape.prototype.getBoundingBox = function() {
      var radiusOnX = this._getRadiusOnAxis(p5.CollisionShape.X_AXIS);
      var radiusOnY = this._getRadiusOnAxis(p5.CollisionShape.Y_AXIS);
      return {
        top: this.center.y - radiusOnY,
        bottom: this.center.y + radiusOnY,
        left: this.center.x - radiusOnX,
        right: this.center.x + radiusOnX,
        width: radiusOnX * 2,
        height: radiusOnY * 2
      };
    };
  
    /**
     * A point collision shape, used to detect overlap and displacement vectors
     * vs other collision shapes.
     * @class p5.PointCollider
     * @constructor
     * @extends p5.CollisionShape
     * @param {p5.Vector} center
     */
    p5.PointCollider = function(center) {
      p5.CollisionShape.call(this, center);
    };
    p5.PointCollider.prototype = Object.create(p5.CollisionShape.prototype);
  
    /**
     * Construct a new PointCollider with given offset for the given sprite.
     * @method createFromSprite
     * @static
     * @param {Sprite} sprite
     * @param {p5.Vector} [offset] from the sprite's center
     * @return {p5.PointCollider}
     */
    p5.PointCollider.createFromSprite = function(sprite, offset) {
      // Create the collision shape at the transformed offset
      var shape = new p5.PointCollider(offset);
      shape.setParentTransform(sprite);
      return shape;
    };
  
    /**
     * Debug-draw this point collider
     * @method draw
     * @param {p5} sketch instance to use for drawing
     */
    p5.PointCollider.prototype.draw = function(sketch) {
      sketch.push();
      sketch.rectMode(sketch.CENTER);
      sketch.translate(this.center.x, this.center.y);
      sketch.noStroke();
      sketch.fill(0, 255, 0);
      sketch.ellipse(0, 0, 2, 2);
      sketch.pop();
    };
  
    /**
     * A Circle collision shape, used to detect overlap and displacement vectors
     * with other collision shapes.
     * @class p5.CircleCollider
     * @constructor
     * @extends p5.CollisionShape
     * @param {p5.Vector} center
     * @param {number} radius
     */
    p5.CircleCollider = function(center, radius) {
      p5.CollisionShape.call(this, center);
  
      /**
       * The unscaled radius of the circle collider.
       * @property radius
       * @type {number}
       */
      this.radius = radius;
  
      /**
       * Final radius of this circle after being scaled by parent and local transforms,
       * cached so we don't recalculate it all the time.
       * @property _scaledRadius
       * @type {number}
       * @private
       */
      this._scaledRadius = 0;
  
      this._computeScaledRadius();
    };
    p5.CircleCollider.prototype = Object.create(p5.CollisionShape.prototype);
  
    /**
     * Construct a new CircleCollider with given offset for the given sprite.
     * @method createFromSprite
     * @static
     * @param {Sprite} sprite
     * @param {p5.Vector} [offset] from the sprite's center
     * @param {number} [radius]
     * @return {p5.CircleCollider}
     */
    p5.CircleCollider.createFromSprite = function(sprite, offset, radius) {
      var customSize = typeof radius === 'number';
      var shape = new p5.CircleCollider(
        offset,
        customSize ? radius : 1
      );
      shape.getsDimensionsFromSprite = !customSize;
      shape.updateFromSprite(sprite);
      return shape;
    };
  
    /**
     * Update this collider based on the properties of a parent Sprite.
     * @method updateFromSprite
     * @param {Sprite} sprite
     * @see p5.CollisionShape.prototype.getsDimensionsFromSprite
     */
    p5.CircleCollider.prototype.updateFromSprite = function(sprite) {
      if (this.getsDimensionsFromSprite) {
        if (sprite.animation) {
          this.radius = Math.max(sprite.animation.getWidth(), sprite.animation.getHeight())/2;
        } else {
          this.radius = Math.max(sprite.width, sprite.height)/2;
        }
      }
      this.setParentTransform(sprite);
    };
  
    /**
     * Recalculate cached properties, relevant vectors, etc. when at least one
     * of the shape's transforms changes.  The base CollisionShape (and PointCollider)
     * only need to recompute the shape's center, but other shapes may need to
     * override this method and do additional recomputation.
     * @method _onTransformChanged
     * @protected
     */
    p5.CircleCollider.prototype._onTransformChanged = function() {
      p5.CollisionShape.prototype._onTransformChanged.call(this);
      this._computeScaledRadius();
    };
  
    /**
     * Call to update the cached scaled radius value.
     * @method _computeScaledRadius
     * @private
     */
    p5.CircleCollider.prototype._computeScaledRadius = function() {
      this._scaledRadius = new p5.Vector(this.radius, 0)
        .transform(this._localTransform)
        .transform(this._parentTransform)
        .sub(this.center)
        .mag();
    };
  
    /**
     * Debug-draw this collision shape.
     * @method draw
     * @param {p5} sketch instance to use for drawing
     */
    p5.CircleCollider.prototype.draw = function(sketch) {
      sketch.push();
      sketch.noFill();
      sketch.stroke(0, 255, 0);
      sketch.rectMode(sketch.CENTER);
      sketch.ellipse(this.center.x, this.center.y, this._scaledRadius*2, this._scaledRadius*2);
      sketch.pop();
    };
  
      /**
     * Overrides CollisionShape.setParentTransform
     * Update this collider's parent transform, which will in turn adjust its
     * position, rotation and scale in world-space and recompute cached values
     * if necessary.
     * If a Sprite is passed as the 'parent' then a new transform will be computed
     * from the sprite's position/rotation/scale and used.
     * Use the max of the x and y scales values so the circle encompasses the sprite.
     * @method setParentTransform
     * @param {p5.Transform2D|Sprite} parent
     */
    p5.CircleCollider.prototype.setParentTransform = function(parent) {
      if (parent instanceof Sprite) {
        this._parentTransform
          .clear()
          .scale(Math.max(parent._getScaleX(), parent._getScaleY()))
          .rotate(radians(parent.rotation))
          .translate(parent.position);
      } else if (parent instanceof p5.Transform2D) {
        this._parentTransform = parent.copy();
      } else {
        throw new TypeError('Bad argument to setParentTransform: ' + parent);
      }
      this._onTransformChanged();
    };
  
    /**
     * Compute candidate separating axes relative to another object.
     * @method _getCandidateAxes
     * @protected
     * @param {p5.CollisionShape} other
     * @return {Array.<p5.Vector>}
     */
    p5.CircleCollider.prototype._getCandidateAxes = function(other) {
      // A circle has infinite potential candidate axes, so the ones we pick
      // depend on what we're colliding against.
  
      // TODO: If we can ask the other shape for a list of vertices, then we can
      //       generalize this algorithm by always using the closest one, and
      //       remove the special knowledge of OBB and AABB.
  
      if (other instanceof p5.OrientedBoundingBoxCollider || other instanceof p5.AxisAlignedBoundingBoxCollider) {
        // There are four possible separating axes with a box - one for each
        // of its vertices, through the center of the circle.
        // We need the closest one.
        var smallestSquareDistance = Infinity;
        var axisToClosestVertex = null;
  
        // Generate the set of vertices for the other shape
        var halfDiagonals = other.halfDiagonals;
        [
          p5.Vector.add(other.center, halfDiagonals[0]),
          p5.Vector.add(other.center, halfDiagonals[1]),
          p5.Vector.sub(other.center, halfDiagonals[0]),
          p5.Vector.sub(other.center, halfDiagonals[1])
        ].map(function(vertex) {
          // Transform each vertex into a vector from this collider center to
          // that vertex, which defines an axis we might want to check.
          return vertex.sub(this.center);
        }.bind(this)).forEach(function(vector) {
          // Figure out which vertex is closest and use its axis
          var squareDistance = vector.magSq();
          if (squareDistance < smallestSquareDistance) {
            smallestSquareDistance = squareDistance;
            axisToClosestVertex = vector;
          }
        });
        return [axisToClosestVertex];
      }
  
      // When checking against another circle or a point we only need to check the
      // axis through both shapes' centers.
      return [p5.Vector.sub(other.center, this.center)];
    };
  
    /**
     * Get this shape's radius (half-width of its projection) along the given axis.
     * @method _getRadiusOnAxis
     * @protected
     * @return {number}
     */
    p5.CircleCollider.prototype._getRadiusOnAxis = function() {
      return this._scaledRadius;
    };
  
    /**
     * Get the shape's minimum radius on any axis for tunneling checks.
     * @method _getMinRadius
     * @protected
     * @param {p5.Vector} axis
     * @return {number}
     */
    p5.CircleCollider.prototype._getMinRadius = function() {
      return this._scaledRadius;
    };
  
    /**
     * An Axis-Aligned Bounding Box (AABB) collision shape, used to detect overlap
     * and compute minimum displacement vectors with other collision shapes.
     *
     * Cannot be rotated - hence the name.  You might use this in place of an
     * OBB because it simplifies some of the math and may improve performance.
     *
     * @class p5.AxisAlignedBoundingBoxCollider
     * @constructor
     * @extends p5.CollisionShape
     * @param {p5.Vector} center
     * @param {number} width
     * @param {number} height
     */
    p5.AxisAlignedBoundingBoxCollider = function(center, width, height) {
      p5.CollisionShape.call(this, center);
  
      /**
       * Unscaled box width.
       * @property _width
       * @private
       * @type {number}
       */
      this._width = width;
  
      /**
       * Unscaled box height.
       * @property _width
       * @private
       * @type {number}
       */
      this._height = height;
  
      /**
       * Cached half-diagonals, used for computing a projected radius.
       * Already transformed into world-space.
       * @property _halfDiagonals
       * @private
       * @type {Array.<p5.Vector>}
       */
      this._halfDiagonals = [];
  
      Object.defineProperties(this, {
  
        /**
         * The untransformed width of the box collider.
         * Recomputes diagonals when set.
         * @property width
         * @type {number}
         */
        'width': {
          enumerable: true,
          get: function() {
            return this._width;
          }.bind(this),
          set: function(w) {
            this._width = w;
            this._halfDiagonals = this._computeHalfDiagonals();
          }.bind(this)
        },
  
        /**
         * The unrotated height of the box collider.
         * Recomputes diagonals when set.
         * @property height
         * @type {number}
         */
        'height': {
          enumerable: true,
          get: function() {
            return this._height;
          }.bind(this),
          set: function(h) {
            this._height = h;
            this._halfDiagonals = this._computeHalfDiagonals();
          }.bind(this)
        },
  
        /**
         * Two vectors representing adjacent half-diagonals of the box at its
         * current dimensions and orientation.
         * @property halfDiagonals
         * @readOnly
         * @type {Array.<p5.Vector>}
         */
        'halfDiagonals': {
          enumerable: true,
          get: function() {
            return this._halfDiagonals;
          }.bind(this)
        }
      });
  
      this._computeHalfDiagonals();
    };
    p5.AxisAlignedBoundingBoxCollider.prototype = Object.create(p5.CollisionShape.prototype);
  
    /**
     * Construct a new AxisAlignedBoundingBoxCollider with given offset for the given sprite.
     * @method createFromSprite
     * @static
     * @param {Sprite} sprite
     * @param {p5.Vector} [offset] from the sprite's center
     * @return {p5.CircleCollider}
     */
    p5.AxisAlignedBoundingBoxCollider.createFromSprite = function(sprite, offset, width, height) {
      var customSize = typeof width === 'number' && typeof height === 'number';
      var box = new p5.AxisAlignedBoundingBoxCollider(
        offset,
        customSize ? width : 1,
        customSize ? height : 1
      );
      box.getsDimensionsFromSprite = !customSize;
      box.updateFromSprite(sprite);
      return box;
    };
  
    /**
     * Update this collider based on the properties of a parent Sprite.
     * @method updateFromSprite
     * @param {Sprite} sprite
     * @see p5.CollisionShape.prototype.getsDimensionsFromSprite
     */
    p5.AxisAlignedBoundingBoxCollider.prototype.updateFromSprite = function(sprite) {
      if (this.getsDimensionsFromSprite) {
        if (sprita.animation) {
          this._width = sprite.animation.getWidth();
          this._height = sprite.animation.getHeight();
        } else {
          this._width = sprite.width;
          this._height = sprite.height;
        }
      }
      this.setParentTransform(sprite);
    };
  
    /**
     * Recalculate cached properties, relevant vectors, etc. when at least one
     * of the shape's transforms changes.  The base CollisionShape (and PointCollider)
     * only need to recompute the shape's center, but other shapes may need to
     * override this method and do additional recomputation.
     * @method _onTransformChanged
     * @protected
     */
    p5.AxisAlignedBoundingBoxCollider.prototype._onTransformChanged = function() {
      p5.CollisionShape.prototype._onTransformChanged.call(this);
      this._computeHalfDiagonals();
    };
  
    /**
     * Recompute this bounding box's half-diagonal vectors.
     * @method _computeHalfDiagonals
     * @private
     * @return {Array.<p5.Vector>}
     */
    p5.AxisAlignedBoundingBoxCollider.prototype._computeHalfDiagonals = function() {
      // We transform the rectangle (which may scale and rotate it) then compute
      // an axis-aligned bounding box _around_ it.
      var composedTransform = p5.Transform2D.mult(this._parentTransform, this._localTransform);
      var transformedDiagonals = [
        new p5.Vector(this._width / 2, -this._height / 2),
        new p5.Vector(this._width / 2, this._height / 2),
        new p5.Vector(-this._width / 2, this._height / 2)
      ].map(function(vertex) {
        return vertex.transform(composedTransform).sub(this.center);
      }.bind(this));
  
      var halfWidth = Math.max(
        Math.abs(transformedDiagonals[0].x),
        Math.abs(transformedDiagonals[1].x)
      );
      var halfHeight = Math.max(
        Math.abs(transformedDiagonals[1].y),
        Math.abs(transformedDiagonals[2].y)
      );
  
      this._halfDiagonals = [
        new p5.Vector(halfWidth, -halfHeight),
        new p5.Vector(halfWidth, halfHeight)
      ];
    };
  
    /**
     * Debug-draw this collider.
     * @method draw
     * @param {p5} sketch - p5 instance to use for drawing
     */
    p5.AxisAlignedBoundingBoxCollider.prototype.draw = function(sketch) {
      sketch.push();
      sketch.rectMode(sketch.CENTER);
      sketch.translate(this.center.x, this.center.y);
      sketch.noFill();
      sketch.stroke(0, 255, 0);
      sketch.strokeWeight(1);
      sketch.rect(0, 0, Math.abs(this._halfDiagonals[0].x) * 2, Math.abs(this._halfDiagonals[0].y) * 2);
      sketch.pop();
    };
  
    /**
     * Compute candidate separating axes relative to another object.
     * @method _getCandidateAxes
     * @protected
     * @return {Array.<p5.Vector>}
     */
    p5.AxisAlignedBoundingBoxCollider.prototype._getCandidateAxes = function() {
      return p5.CollisionShape.WORLD_AXES;
    };
  
    /**
     * Get this shape's radius (half-width of its projection) along the given axis.
     * @method _getRadiusOnAxis
     * @protected
     * @param {p5.Vector} axis
     * @return {number}
     */
    p5.AxisAlignedBoundingBoxCollider.prototype._getRadiusOnAxis = function(axis) {
      // How to project a rect onto an axis:
      // Project the center-corner vectors for two adjacent corners (cached here)
      // onto the axis.  The larger magnitude of the two is your projection's radius.
      return Math.max(
        p5.Vector.project(this._halfDiagonals[0], axis).mag(),
        p5.Vector.project(this._halfDiagonals[1], axis).mag());
    };
  
    /**
     * Get the shape's minimum radius on any axis for tunneling checks.
     * @method _getMinRadius
     * @protected
     * @param {p5.Vector} axis
     * @return {number}
     */
    p5.AxisAlignedBoundingBoxCollider.prototype._getMinRadius = function() {
      return Math.min(this._width, this._height);
    };
  
    /**
     * An Oriented Bounding Box (OBB) collision shape, used to detect overlap and
     * compute minimum displacement vectors with other collision shapes.
     * @class p5.OrientedBoundingBoxCollider
     * @constructor
     * @extends p5.CollisionShape
     * @param {p5.Vector} center of the rectangle in world-space
     * @param {number} width of the rectangle (when not rotated)
     * @param {number} height of the rectangle (when not rotated)
     * @param {number} rotation about center, in radians
     */
    p5.OrientedBoundingBoxCollider = function(center, width, height, rotation) {
      p5.CollisionShape.call(this, center, rotation);
  
      /**
       * Unscaled box width.
       * @property _width
       * @private
       * @type {number}
       */
      this._width = width;
  
      /**
       * Unscaled box height.
       * @property _width
       * @private
       * @type {number}
       */
      this._height = height;
  
      /**
       * Cached separating axes this shape contributes to a collision.
       * @property _potentialAxes
       * @private
       * @type {Array.<p5.Vector>}
       */
      this._potentialAxes = [];
  
      /**
       * Cached half-diagonals, used for computing a projected radius.
       * Already transformed into world-space.
       * @property _halfDiagonals
       * @private
       * @type {Array.<p5.Vector>}
       */
      this._halfDiagonals = [];
  
      Object.defineProperties(this, {
  
        /**
         * The unrotated width of the box collider.
         * Recomputes diagonals when set.
         * @property width
         * @type {number}
         */
        'width': {
          enumerable: true,
          get: function() {
            return this._width;
          }.bind(this),
          set: function(w) {
            this._width = w;
            this._onTransformChanged();
          }.bind(this)
        },
  
        /**
         * The unrotated height of the box collider.
         * Recomputes diagonals when set.
         * @property height
         * @type {number}
         */
        'height': {
          enumerable: true,
          get: function() {
            return this._height;
          }.bind(this),
          set: function(h) {
            this._height = h;
            this._onTransformChanged();
          }.bind(this)
        },
  
        /**
         * Two vectors representing adjacent half-diagonals of the box at its
         * current dimensions and orientation.
         * @property halfDiagonals
         * @readOnly
         * @type {Array.<p5.Vector>}
         */
        'halfDiagonals': {
          enumerable: true,
          get: function() {
            return this._halfDiagonals;
          }.bind(this)
        }
      });
  
      this._onTransformChanged();
    };
    p5.OrientedBoundingBoxCollider.prototype = Object.create(p5.CollisionShape.prototype);
  
    /**
     * Construct a new AxisAlignedBoundingBoxCollider with given offset for the given sprite.
     * @method createFromSprite
     * @static
     * @param {Sprite} sprite
     * @param {p5.Vector} [offset] from the sprite's center
     * @param {number} [width]
     * @param {number} [height]
     * @param {number} [rotation] in radians
     * @return {p5.CircleCollider}
     */
    p5.OrientedBoundingBoxCollider.createFromSprite = function(sprite, offset, width, height, rotation) {
      var customSize = typeof width === 'number' && typeof height === 'number';
      var box = new p5.OrientedBoundingBoxCollider(
        offset,
        customSize ? width : 1,
        customSize ? height : 1,
        rotation
      );
      box.getsDimensionsFromSprite = !customSize;
      box.updateFromSprite(sprite);
      return box;
    };
  
    /**
     * Update this collider based on the properties of a parent Sprite.
     * @method updateFromSprite
     * @param {Sprite} sprite
     * @see p5.CollisionShape.prototype.getsDimensionsFromSprite
     */
    p5.OrientedBoundingBoxCollider.prototype.updateFromSprite =
      p5.AxisAlignedBoundingBoxCollider.prototype.updateFromSprite;
  
    /**
     * Assuming this collider is a sprite's swept collider, update it based on
     * the properties of the parent sprite so that it encloses the sprite's
     * current position and its projected position.
     * @method updateSweptColliderFromSprite
     * @param {Sprite} sprite
     */
    p5.OrientedBoundingBoxCollider.prototype.updateSweptColliderFromSprite = function(sprite) {
      var vMagnitude = sprite.velocity.mag();
      var vPerpendicular = new p5.Vector(sprite.velocity.y, -sprite.velocity.x);
      this._width = vMagnitude + 2 * sprite.collider._getRadiusOnAxis(sprite.velocity);
      this._height = 2 * sprite.collider._getRadiusOnAxis(vPerpendicular);
      var newRotation = radians(sprite.getDirection());
      var newCenter = new p5.Vector(
        sprite.newPosition.x + 0.5 * sprite.velocity.x,
        sprite.newPosition.y + 0.5 * sprite.velocity.y
      );
      // Perform this.rotation = newRotation and this.center = newCenter;
      this._localTransform
        .clear()
        .scale(this._scale)
        .rotate(newRotation)
        .translate(this._offset)
        .translate(p5.Vector.mult(this._center, -1))
        .translate(newCenter);
      this._onTransformChanged();
    };
  
    /**
     * Recalculate cached properties, relevant vectors, etc. when at least one
     * of the shape's transforms changes.  The base CollisionShape (and PointCollider)
     * only need to recompute the shape's center, but other shapes may need to
     * override this method and do additional recomputation.
     * @method _onTransformChanged
     * @protected
     */
    p5.OrientedBoundingBoxCollider.prototype._onTransformChanged = function() {
      p5.CollisionShape.prototype._onTransformChanged.call(this);
  
      // Transform each vertex by the local and global matrices
      // then use their differences to determine width, height, and halfDiagonals
      var composedTransform = p5.Transform2D.mult(this._parentTransform, this._localTransform);
      var transformedVertices = [
        new p5.Vector(this._width / 2, -this._height / 2),
        new p5.Vector(this._width / 2, this._height / 2),
        new p5.Vector(-this._width / 2, this._height / 2)
      ].map(function(vertex) {
        return vertex.transform(composedTransform);
      });
  
      this._halfDiagonals = [
        p5.Vector.sub(transformedVertices[0], this.center),
        p5.Vector.sub(transformedVertices[1], this.center)
      ];
  
      this._potentialAxes = [
        p5.Vector.sub(transformedVertices[1], transformedVertices[2]),
        p5.Vector.sub(transformedVertices[1], transformedVertices[0])
      ];
    };
  
    /**
     * Debug-draw this collider.
     * @method draw
     * @param {p5} sketch - p5 instance to use for drawing
     */
    p5.OrientedBoundingBoxCollider.prototype.draw = function(sketch) {
      var composedTransform = p5.Transform2D.mult(this._localTransform, this._parentTransform);
      var scale = composedTransform.getScale();
      var rotation = composedTransform.getRotation();
      sketch.push();
      sketch.translate(this.center.x, this.center.y);
      sketch.scale(scale.x, scale.y);
      if (sketch._angleMode === sketch.RADIANS) {
        sketch.rotate(rotation);
      } else {
        sketch.rotate(degrees(rotation));
      }
  
      sketch.noFill();
      sketch.stroke(0, 255, 0);
      sketch.strokeWeight(1);
      sketch.rectMode(sketch.CENTER);
      sketch.rect(0, 0, this._width, this._height);
      sketch.pop();
    };
  
    /**
     * Compute candidate separating axes relative to another object.
     * @method _getCandidateAxes
     * @protected
     * @return {Array.<p5.Vector>}
     */
    p5.OrientedBoundingBoxCollider.prototype._getCandidateAxes = function() {
      // An oriented bounding box always provides two of its face normals,
      // which we've precomputed.
      return this._potentialAxes;
    };
  
    /**
     * Get this shape's radius (half-width of its projection) along the given axis.
     * @method _getRadiusOnAxis
     * @protected
     * @param {p5.Vector} axis
     * @return {number}
     */
    p5.OrientedBoundingBoxCollider.prototype._getRadiusOnAxis =
      p5.AxisAlignedBoundingBoxCollider.prototype._getRadiusOnAxis;
    // We can reuse the AABB version of this method because both are projecting
    // cached half-diagonals - the same code works.
  
    /**
     * When checking for tunneling through a OrientedBoundingBoxCollider use a
     * worst-case of zero (e.g. if the other sprite is passing through a corner).
     * @method _getMinRadius
     * @protected
     * @param {p5.Vector} axis
     * @return {number}
     */
    p5.OrientedBoundingBoxCollider.prototype._getMinRadius =
      p5.AxisAlignedBoundingBoxCollider.prototype._getMinRadius;
  
    /**
     * A 2D affine transformation (translation, rotation, scale) stored as a
     * 3x3 matrix that uses homogeneous coordinates.  Used to quickly transform
     * points or vectors between reference frames.
     * @class p5.Transform2D
     * @constructor
     * @extends Array
     * @param {p5.Transform2D|Array.<number>} [source]
     */
    p5.Transform2D = function(source) {
      // We only store the first six values.
      // the last row in a 2D transform matrix is always "0 0 1" so we can
      // save space and speed up certain calculations with this assumption.
      source = source || [1, 0, 0, 0, 1, 0];
      if (source.length !== 6) {
        throw new TypeError('Transform2D must have six components');
      }
      this.length = 6;
      this[0] = source[0];
      this[1] = source[1];
      this[2] = source[2];
      this[3] = source[3];
      this[4] = source[4];
      this[5] = source[5];
    };
    p5.Transform2D.prototype = Object.create(Array.prototype);
  
    /**
     * Reset this transform to an identity transform, in-place.
     * @method clear
     * @return {p5.Transform2D} this transform
     */
    p5.Transform2D.prototype.clear = function() {
      this[0] = 1;
      this[1] = 0;
      this[2] = 0;
      this[3] = 0;
      this[4] = 1;
      this[5] = 0;
      return this;
    };
  
    /**
     * Make a copy of this transform.
     * @method copy
     * @return {p5.Transform2D}
     */
    p5.Transform2D.prototype.copy = function() {
      return new p5.Transform2D(this);
    };
  
    /**
     * Check whether two transforms are the same.
     * @method equals
     * @param {p5.Transform2D|Array.<number>} other
     * @return {boolean}
     */
    p5.Transform2D.prototype.equals = function(other) {
      if (!(other instanceof p5.Transform2D || Array.isArray(other))) {
        return false; // Never equal to other types.
      }
  
      for (var i = 0; i < 6; i++) {
        if (this[i] !== other[i]) {
          return false;
        }
      }
      return true;
    };
  
    /**
     * Multiply two transforms together, combining them.
     * Does not modify original transforms.  Assigns result into dest argument if
     * provided and returns it.  Otherwise returns a new transform.
     * @method mult
     * @static
     * @param {p5.Transform2D|Array.<number>} t1
     * @param {p5.Transform2D|Array.<number>} t2
     * @param {p5.Transform2D} [dest]
     * @return {p5.Transform2D}
     */
    p5.Transform2D.mult = function(t1, t2, dest) {
      dest = dest || new p5.Transform2D();
  
      // Capture values of original matrices in local variables, in case one of
      // them is the one we're mutating.
      var t1_0, t1_1, t1_2, t1_3, t1_4, t1_5;
      t1_0 = t1[0];
      t1_1 = t1[1];
      t1_2 = t1[2];
      t1_3 = t1[3];
      t1_4 = t1[4];
      t1_5 = t1[5];
  
      var t2_0, t2_1, t2_2, t2_3, t2_4, t2_5;
      t2_0 = t2[0];
      t2_1 = t2[1];
      t2_2 = t2[2];
      t2_3 = t2[3];
      t2_4 = t2[4];
      t2_5 = t2[5];
  
      dest[0] = t1_0*t2_0 + t1_1*t2_3;
      dest[1] = t1_0*t2_1 + t1_1*t2_4;
      dest[2] = t1_0*t2_2 + t1_1*t2_5 + t1_2;
  
      dest[3] = t1_3*t2_0 + t1_4*t2_3;
      dest[4] = t1_3*t2_1 + t1_4*t2_4;
      dest[5] = t1_3*t2_2 + t1_4*t2_5 + t1_5;
  
      return dest;
    };
  
    /**
     * Multiply this transform by another, combining them.
     * Modifies this transform and returns it.
     * @method mult
     * @param {p5.Transform2D|Float32Array|Array.<number>} other
     * @return {p5.Transform2D}
     */
    p5.Transform2D.prototype.mult = function(other) {
      return p5.Transform2D.mult(this, other, this);
    };
  
    /**
     * Modify this transform, translating it by a certain amount.
     * Returns this transform.
     * @method translate
     * @return {p5.Transform2D}
     * @example
     *     // Two different ways to call this method.
     *     var t = new p5.Transform();
     *     // 1. Two numbers
     *     t.translate(x, y);
     *     // 2. One vector
     *     t.translate(new p5.Vector(x, y));
     */
    p5.Transform2D.prototype.translate = function(arg0, arg1) {
      var x, y;
      if (arg0 instanceof p5.Vector) {
        x = arg0.x;
        y = arg0.y;
      } else if (typeof arg0 === 'number' && typeof arg1 === 'number') {
        x = arg0;
        y = arg1;
      } else {
        var args = '';
        for (var i = 0; i < arguments.length; i++) {
          args += arguments[i] + ', ';
        }
        throw new TypeError('Invalid arguments to Transform2D.translate: ' + args);
      }
      return p5.Transform2D.mult([
        1, 0, x,
        0, 1, y
      ], this, this);
    };
  
    /**
     * Retrieve the resolved translation of this transform.
     * @method getTranslation
     * @return {p5.Vector}
     */
    p5.Transform2D.prototype.getTranslation = function() {
      return new p5.Vector(this[2], this[5]);
    };
  
    /**
     * Modify this transform, scaling it by a certain amount.
     * Returns this transform.
     * @method scale
     * @return {p5.Transform2D}
     * @example
     *     // Three different ways to call this method.
     *     var t = new p5.Transform();
     *     // 1. One scalar value
     *     t.scale(uniformScale);
     *     // 1. Two scalar values
     *     t.scale(scaleX, scaleY);
     *     // 2. One vector
     *     t.translate(new p5.Vector(scaleX, scaleY));
     */
    p5.Transform2D.prototype.scale = function(arg0, arg1) {
      var sx, sy;
      if (arg0 instanceof p5.Vector) {
        sx = arg0.x;
        sy = arg0.y;
      } else if (typeof arg0 === 'number' && typeof arg1 === 'number') {
        sx = arg0;
        sy = arg1;
      } else if (typeof arg0 === 'number') {
        sx = arg0;
        sy = arg0;
      } else {
        throw new TypeError('Invalid arguments to Transform2D.scale: ' + arguments);
      }
      return p5.Transform2D.mult([
        sx, 0, 0,
        0, sy, 0
      ], this, this);
    };
  
    /**
     * Retrieve the scale vector of this transform.
     * @method getScale
     * @return {p5.Vector}
     */
    p5.Transform2D.prototype.getScale = function() {
      var a = this[0], b = this[1],
          c = this[3], d = this[4];
      return new p5.Vector(
        sign(a) * Math.sqrt(a*a + b*b),
        sign(d) * Math.sqrt(c*c + d*d)
      );
    };
  
    /*
     * Return -1, 0, or 1 depending on whether a number is negative, zero, or positive.
     */
    function sign(x) {
      x = +x; // convert to a number
      if (x === 0 || isNaN(x)) {
        return Number(x);
      }
      return x > 0 ? 1 : -1;
    }
  
    /**
     * Modify this transform, rotating it by a certain amount.
     * @method rotate
     * @param {number} radians
     * @return {p5.Transform2D}
     */
    p5.Transform2D.prototype.rotate = function(radians) {
      // Clockwise!
      if (typeof radians !== 'number') {
        throw new TypeError('Invalid arguments to Transform2D.rotate: ' + arguments);
      }
      var sinR = Math.sin(radians);
      var cosR = Math.cos(radians);
      return p5.Transform2D.mult([
        cosR, -sinR, 0,
        sinR, cosR, 0
      ], this, this);
    };
  
    /**
     * Retrieve the angle of this transform in radians.
     * @method getRotation
     * @return {number}
     */
    p5.Transform2D.prototype.getRotation = function() {
      // see http://math.stackexchange.com/a/13165
      return Math.atan2(-this[1], this[0]);
    };
  
    /**
     * Applies a 2D transformation matrix (using homogeneous coordinates, so 3x3)
     * to a Vector2 (<x, y, 1>) and returns a new vector2.
     * @method transform
     * @for p5.Vector
     * @static
     * @param {p5.Vector} v
     * @param {p5.Transform2D} t
     * @return {p5.Vector} a new vector
     */
    p5.Vector.transform = function(v, t) {
      return v.copy().transform(t);
    };
  
    /**
     * Transforms this vector by a 2D transformation matrix.
     * @method transform
     * @for p5.Vector
     * @param {p5.Transform2D} transform
     * @return {p5.Vector} this, after the change
     */
    p5.Vector.prototype.transform = function(transform) {
      // Note: We cheat a whole bunch here since this is just 2D!
      // Use a different method if looking for true matrix multiplication.
      var x = this.x;
      var y = this.y;
      this.x = transform[0]*x + transform[1]*y + transform[2];
      this.y = transform[3]*x + transform[4]*y + transform[5];
      return this;
    };
  
  }));
  