(function(win) {

    // Constants
  
    var PRECISION       = 1e2; // 2 decimals
    var VENDOR_PREFIXES = ['webkit','moz', ''];
    var SVG_NAMESPACE   = 'http://www.w3.org/2000/svg';
    var CSS_PREFIX      = 'peel-';
  
    var clipProperty, transformProperty, boxShadowProperty, filterProperty;
    var backgroundGradientSupport;
    var docEl = document.documentElement;
    var style = docEl.style;
  
  
    // Support
  
    function getCssProperty(name) {
      var prefix, str;
      for (var i = 0; i < VENDOR_PREFIXES.length; i++) {
        prefix = VENDOR_PREFIXES[i];
        str = prefix ? prefix + capitalize(name) : name;
        if (str in style) {
          return str;
        }
      }
    }
  
    function setCssProperties() {
      clipProperty      = getCssProperty('clipPath');
      transformProperty = getCssProperty('transform');
      boxShadowProperty = getCssProperty('boxShadow');
      filterProperty    = getCssProperty('filter');
      setBackgroundGradientSupport();
      Peel.supported = !!(clipProperty && transformProperty);
      Peel.effectsSupported = backgroundGradientSupport;
    }
  
    function setBackgroundGradientSupport() {
      var el = document.createElement('div');
      var style = el.style;
      style.cssText = 'background:linear-gradient(45deg,#9f9,white);';
      backgroundGradientSupport = (style.backgroundImage || '').indexOf('gradient') > -1;
    }
  
  
  
    // General helpers
  
    function round(n) {
      return Math.round(n * PRECISION) / PRECISION;
    }
  
    // Clamps the number to be between 0 and 1.
    function clamp(n) {
      return Math.max(0, Math.min(1, n));
    }
  
    function normalize(n, min, max) {
      return (n - min) / (max - min);
    }
  
    // Distributes a number between 0 and 1 along a bell curve.
    function distribute(t, mult) {
      return (mult || 1) * 2 * (.5 - Math.abs(t - .5));
    }
  
    function capitalize(str) {
      return str.slice(0,1).toUpperCase() + str.slice(1);
    }
  
    function camelize(str) {
      return str.replace(/-(\w)/g, function(a, b) {
        return b.toUpperCase();
      });
    }
  
    function prefix(str) {
      return CSS_PREFIX + str;
    }
  
    // CSS Helpers
  
    function setCSSClip(el, clip) {
      el.style[clipProperty] = clip;
    }
  
    function setTransform(el, t) {
      el.style[transformProperty] = t;
    }
  
    function setBoxShadow(el, x, y, blur, spread, intensity) {
      el.style[boxShadowProperty] = getShadowCss(x, y, blur, spread, intensity);
    }
  
    function setDropShadow(el, x, y, blur, intensity) {
      el.style[filterProperty] = 'drop-shadow(' + getShadowCss(x, y, blur, null, intensity) + ')';
    }
  
    function getShadowCss(x, y, blur, spread, intensity) {
      return round(x) + 'px ' +
             round(y) + 'px ' +
             round(blur) + 'px ' +
             (spread ? round(spread) + 'px ' : '') +
             'rgba(0,0,0,' + round(intensity) + ')';
    }
  
    function setOpacity(el, t) {
      el.style.opacity = t;
    }
  
    function setBackgroundGradient(el, rotation, stops) {
      if (!backgroundGradientSupport) return;
      var css;
      if (stops.length === 0) {
        css = 'none';
      } else {
        css = 'linear-gradient(' + round(rotation) + 'deg,' + stops.join(',') + ')';
      }
      el.style.backgroundImage = css;
    }
  
    // Event Helpers
  
    function addEvent(el, type, fn) {
      el.addEventListener(type, fn)
    }
  
    function removeEvent(el, type, fn) {
      el.removeEventListener(type, fn);
    }
  
    function getEventCoordinates(evt, el) {
      var pos = evt.changedTouches ? evt.changedTouches[0] : evt;
      return {
        'x': pos.clientX - el.offsetLeft + window.scrollX,
        'y': pos.clientY - el.offsetTop + window.scrollY
      }
    }
  
    function bindWithEvent(fn, scope, arg1, arg2) {
      return function(evt) {
        fn.call(scope, evt, arg1, arg2);
      }
    }
  
    // Color Helpers
  
    function getBlackStop(a, pos) {
      return getColorStop(0, 0, 0, a, pos);
    }
  
    function getWhiteStop(a, pos) {
      return getColorStop(255, 255, 255, a, pos);
    }
  
    function getColorStop(r, g, b, a, pos) {
      a = round(clamp(a));
      return 'rgba('+ r +','+ g +','+ b +','+ a +') ' + round(pos * 100) + '%';
    }
  
  
    // DOM Element Helpers
  
    function getElement(obj, node) {
      if (typeof obj === 'string') {
        obj = (node || document).querySelector(obj);
      }
      return obj;
    }
  
    function createElement(parent, className) {
      var el = document.createElement('div');
      addClass(el, className);
      parent.appendChild(el);
      return el;
    }
  
    function removeClass(el, str) {
      el.classList.remove(str);
    }
  
    function addClass(el, str) {
      el.classList.add(str);
    }
  
    function getZIndex(el) {
      return el.style.zIndex;
    }
  
    function setZIndex(el, index) {
      el.style.zIndex = index;
    }
  
  
    // SVG Helpers
  
    function createSVGElement(tag, parent, attributes) {
      parent = parent || docEl;
      var el = document.createElementNS(SVG_NAMESPACE, tag);
      parent.appendChild(el);
      for (var key in attributes) {
        if (!attributes.hasOwnProperty(key)) continue;
        setSVGAttribute(el, key, attributes[key]);
      }
      return el;
    }
  
    function setSVGAttribute(el, key, value) {
      el.setAttributeNS(null, key, value);
    }
  
  
    /**
     * Main class that controls the peeling effect.
     * @param {HTMLElement|string} el The main container element (can be query).
     * @param {object} options Options for the effect.
     * @constructor
     * @public
     */
    function Peel (el, opt) {
      this.setOptions(opt);
      this.el = getElement(el, docEl);
      this.constraints = [];
      this.events = [];
      this.setupLayers();
      this.setupDimensions();
      this.setCorner(this.getOption('corner'));
      this.setMode(this.getOption('mode'));
      this.init();
    }
  
    /**
     * Four constants representing the corners of the element from which peeling can occur.
     * @constant
     * @public
     */
    Peel.Corners = {
      TOP_LEFT:     0x0,
      TOP_RIGHT:    0x1,
      BOTTOM_LEFT:  0x2,
      BOTTOM_RIGHT: 0x3
    }
  
    /**
     * Defaults
     * @constant
     */
    Peel.Defaults = {
      'topShadow': true,
      'topShadowBlur': 5,
      'topShadowAlpha': .5,
      'topShadowOffsetX': 0,
      'topShadowOffsetY': 1,
      'topShadowCreatesShape': true,
  
      'backReflection': false,
      'backReflectionSize': .02,
      'backReflectionOffset': 0,
      'backReflectionAlpha': .15,
      'backReflectionDistribute': true,
  
      'backShadow': true,
      'backShadowSize': .04,
      'backShadowOffset': 0,
      'backShadowAlpha': .1,
      'backShadowDistribute': true,
  
      'bottomShadow': true,
      'bottomShadowSize': 1.5,
      'bottomShadowOffset': 0,
      'bottomShadowDarkAlpha': .7,
      'bottomShadowLightAlpha': .1,
      'bottomShadowDistribute': true,
  
      'setPeelOnInit': true,
      'clippingBoxScale': 4,
      'flipConstraintOffset': 5,
      'dragPreventsDefault': true
    }
  
    /**
     * Sets the corner for the peel effect to happen from (default is bottom right).
     * @param {Mixed} [...] Either x,y or a corner id.
     * @public
     */
    Peel.prototype.setCorner = function() {
      var args = arguments;
      if (args[0] === undefined) {
        args = [Peel.Corners.BOTTOM_RIGHT];
      } else if (args[0].length) {
        args = args[0];
      }
      this.corner = this.getPointOrCorner(args);
    }
  
    /**
     * Sets a pre-defined "mode".
     * @param {string} mode The mode to set.
     * @public
     */
    Peel.prototype.setMode = function(mode) {
      if (mode === 'book') {
        // The order of constraints is important here so that the peel line
        // approaches the horizontal smoothly without jumping.
        this.addPeelConstraint(Peel.Corners.BOTTOM_LEFT);
        this.addPeelConstraint(Peel.Corners.TOP_LEFT);
        // Removing effect distribution will make the book still have some
        // depth to the effect while fully open.
        this.setOption('backReflection', false);
        this.setOption('backShadowDistribute', false);
        this.setOption('bottomShadowDistribute', false);
      } else if (mode === 'calendar') {
        this.addPeelConstraint(Peel.Corners.TOP_RIGHT);
        this.addPeelConstraint(Peel.Corners.TOP_LEFT);
      }
    }
  
    /**
     * Sets a path along which the peel will follow.
     * Can be a flat line segment or a bezier curve.
     * @param {...number} x/y Points along the path. 4 arguments indicates a
     *     linear path along 2 points (p1 to p2), while 8 arguments indicates a
     *     bezier curve from p1 to p2 using control points c1 and c2. The first
     *     and last two arguments represent p1 and p2, respectively.
     * @public
     */
    Peel.prototype.setPeelPath = function(x1, y1) {
      var args = arguments, p1, p2, c1, c2;
      p1 = new Point(x1, y1);
      if (args.length === 4) {
        p2 = new Point(args[2], args[3]);
        this.path = new LineSegment(p1, p2);
      } else if (args.length === 8) {
        c1 = new Point(args[2], args[3]);
        c2 = new Point(args[4], args[5]);
        p2 = new Point(args[6], args[7]);
        this.path = new BezierCurve(p1, c1, c2, p2);
      }
    }
  
    /**
     * Sets a function to be called when the user drags, either with a mouse or
     * with a finger (touch events).
     * @param {Function} fn The function to be called on drag. This function will
     *     be called with the Peel instance as the "this" keyword, the original
     *     event as the first argument, and the x, y coordinates of the drag as
     *     the 2nd and 3rd arguments, respectively.
     * @param {HTMLElement} el The element to initiate the drag on mouse/touch start.
     *     If not passed, this will be the element associated with the Peel
     *     instance. Allowing this to be passed lets another element serve as a
     *     "hit area" that can be larger than the element itself.
     * @public
     */
    Peel.prototype.handleDrag = function(fn, el) {
      this.dragHandler = fn;
      this.setupDragEvents(el);
    }
  
    /**
     * Sets a function to be called when the user either clicks with a mouse or
     * taps with a finger (touch events).
     * @param {Function} fn The function to be called on press. This function will
     *     be called with the Peel instance as the "this" keyword, the original
     *     event as the first argument, and the x, y coordinates of the event as
     *     the 2nd and 3rd arguments, respectively.
     * @param {HTMLElement} el The element to initiate the event.
     *     If not passed, this will be the element associated with the Peel
     *     instance. Allowing this to be passed lets another element serve as a
     *     "hit area" that can be larger than the element itself.
     * @public
     */
    Peel.prototype.handlePress = function(fn, el) {
      this.pressHandler = fn;
      this.setupDragEvents(el);
    }
  
    /**
     * Sets up the drag events needed for both drag and press handlers.
     * @param {HTMLElement} el The element to initiate the dragStart event on.
     * @private
     */
    Peel.prototype.setupDragEvents = function(el) {
      var self = this, isDragging, moveName, endName;
  
      if (this.dragEventsSetup) {
        return;
      }
  
      el = el || this.el;
  
      function dragStart (touch, evt) {
        if (self.getOption('dragPreventsDefault')) {
          evt.preventDefault();
        }
        moveName = touch ? 'touchmove' : 'mousemove';
        endName  = touch ? 'touchend' : 'mouseup';
  
        addEvent(docEl, moveName, dragMove);
        addEvent(docEl, endName, dragEnd);
        isDragging = false;
      }
  
      function dragMove (evt) {
        if (self.dragHandler) {
          callHandler(self.dragHandler, evt);
        }
        isDragging = true;
      }
  
      function dragEnd(evt) {
        if (!isDragging && self.pressHandler) {
          callHandler(self.pressHandler, evt);
        }
        removeEvent(docEl, moveName, dragMove);
        removeEvent(docEl, endName, dragEnd);
      }
  
      function callHandler(fn, evt) {
        var coords = getEventCoordinates(evt, self.el);
        fn.call(self, evt, coords.x, coords.y);
      }
  
      this.addEvent(el, 'mousedown', dragStart.bind(this, false));
      this.addEvent(el, 'touchstart', dragStart.bind(this, true));
      this.dragEventsSetup = true;
    }
  
    /**
     * Remove all event handlers previously added to the instance.
     * @public
     */
    Peel.prototype.removeEvents = function() {
      this.events.forEach(function(e, i) {
        removeEvent(e.el, e.type, e.handler);
      });
      this.events = [];
    }
  
    /**
     * Sets the peel effect to a point in time along a previously
     * specified path. Will throw an error if no path exists.
     * @param {number} n The time value (between 0 and 1).
     * @public
     */
    Peel.prototype.setTimeAlongPath = function(t) {
      t = clamp(t);
      var point = this.path.getPointForTime(t);
      this.timeAlongPath = t;
      this.setPeelPosition(point.x, point.y);
    }
  
    /**
     * Sets a threshold above which the top layer (including the backside) layer
     * will begin to fade out. This is calculated based on the visible clipped
     * area of the polygon. If a peel path is set, it will use the progress along
     * the path instead.
     * @param {number} n A point between 0 and 1.
     * @public
     */
    Peel.prototype.setFadeThreshold = function(n) {
      this.fadeThreshold = n;
    }
  
    /**
     * Sets the position of the peel effect. This point is the position
     * of the corner that is being peeled back.
     * @param {Mixed} [...] Either x,y or a corner id.
     * @public
     */
    Peel.prototype.setPeelPosition = function() {
      var pos = this.getPointOrCorner(arguments);
      pos = this.getConstrainedPeelPosition(pos);
      if (!pos) {
        return;
      }
      this.peelLineSegment = this.getPeelLineSegment(pos);
      this.peelLineRotation = this.peelLineSegment.getAngle();
      this.setClipping();
      this.setBackTransform(pos);
      this.setEffects();
    }
  
    /**
     * Sets a constraint on the distance of the peel. This can be thought of as a
     * point on the layers that are connected and cannot be torn apart. Typically
     * this only makes sense as a point on the outer edge, such as the left edge
     * of an open book, or the top edge of a calendar. In this case, simply using
     * 2 constraint points (top-left/bottom-left for a book, etc) will create the
     * desired effect. An arbitrary point can also be used with an effect like a
     * thumbtack holding the pages together.
     * @param {Mixed} [...] Either x,y or a corner id.
     * @public
     */
    /**
     * Sets the corner for the peel effect to happen from.
     * @public
     */
    Peel.prototype.addPeelConstraint = function() {
      var p = this.getPointOrCorner(arguments);
      var radius = this.corner.subtract(p).getLength();
      this.constraints.push(new Circle(p, radius));
      this.calculateFlipConstraint();
    }
  
    /**
     * Sets an option to use for the effect.
     * @param {string} key The option to set.
     * @param {Mixed} value The value for the option.
     * @public
     */
    Peel.prototype.setOption = function(key, value) {
      this.options[key] = value;
    }
  
    /**
     * Gets an option set by the user.
     * @param {string} key The key of the option to get.
     * @returns {Mixed}
     * @public
     */
    Peel.prototype.getOption = function(key) {
      return this.options[camelize(key)];
    }
  
    /**
     * Gets the ratio of the area of the clipped top layer to the total area.
     * @returns {number} A value between 0 and 1.
     * @public
     */
    Peel.prototype.getAmountClipped = function() {
      var topArea = this.getTopClipArea();
      var totalArea = this.width * this.height;
      return normalize(topArea, totalArea, 0);
    }
  
    /**
     * Adds an event listener to the element and keeps track of it for later
     * removal.
     * @param {Element} el The element to add the handler to.
     * @param {string} type The event type.
     * @param {Function} fn The handler function.
     * @private
     */
    Peel.prototype.addEvent = function(el, type, fn) {
      addEvent(el, type, fn);
      this.events.push({
        el: el,
        type: type,
        handler: fn
      });
      return fn;
    }
    /**
     * Gets the area of the clipped top layer.
     * @returns {number}
     * @private
     */
    Peel.prototype.getTopClipArea = function() {
      var top  = new Polygon();
      this.elementBox.forEach(function(side) {
        this.distributeLineByPeelLine(side, top);
      }, this);
      return Polygon.getArea(top.getPoints());
    }
  
    /**
     * Determines which of the constraints should be used as the flip constraint
     * by checking which has a y value closes to the corner (because the
     * constraint operates relative to the vertical midline). Only one constraint
     * should be required - changing the order of the constraints can help to
     * achieve the proper effect and more than one will interfere with each other.
     * @private
     */
    Peel.prototype.calculateFlipConstraint = function() {
      var corner = this.corner, arr = this.constraints.concat();
      this.flipConstraint = arr.sort(function(a, b) {
        var aY = corner.y - a.center.y;
        var bY = corner.y - b.center.y;
        return a - b;
      })[0];
    }
  
    /**
     * Called when the drag event starts.
     * @param {Event} evt The original DOM event.
     * @param {string} type The event type, "mouse" or "touch".
     * @param {Function} fn The handler function to be called on drag.
     * @private
     */
    Peel.prototype.dragStart = function(evt, type, fn) {
    }
  
    /**
     * Calls an event handler using the coordinates of the event.
     * @param {Event} evt The original event.
     * @param {Function} fn The handler to call.
     * @private
     */
    Peel.prototype.fireHandler = function(evt, fn) {
      var coords = getEventCoordinates(evt, this.el);
      fn.call(this, evt, coords.x, coords.y);
    }
  
    /**
     * Sets the clipping points of the top and back layers based on a line
     * segment that represents the peel line.
     * @private
     */
    Peel.prototype.setClipping = function() {
      var top  = new Polygon();
      var back = new Polygon();
      this.clippingBox.forEach(function(side) {
        this.distributeLineByPeelLine(side, top, back);
      }, this);
  
      this.topClip.setPoints(top.getPoints());
      this.backClip.setPoints(back.getPoints());
    }
  
    /**
     * Distributes the first point in the given line segment and its intersect
     * with the peel line, if there is one.
     * @param {LineSegment} seg The line segment to check against.
     * @param {Polygon} poly1 The first polygon.
     * @param {Polygon} [poly2] The second polygon.
     * @private
     */
    Peel.prototype.distributeLineByPeelLine = function(seg, poly1, poly2) {
      var intersect = this.peelLineSegment.getIntersectPoint(seg);
      this.distributePointByPeelLine(seg.p1, poly1, poly2);
      this.distributePointByPeelLine(intersect, poly1, poly2);
    }
  
    /**
     * Distributes the given point to one of two polygons based on which side of
     * the peel line it falls upon (if it falls directly on the line segment
     * it is added to both).
     * @param {Point} p The point to be distributed.
     * @param {Polygon} poly1 The first polygon.
     * @param {Polygon} [poly2] The second polygon.
     * @private
     */
    Peel.prototype.distributePointByPeelLine = function(p, poly1, poly2) {
      if (!p) return;
      var d = this.peelLineSegment.getPointDeterminant(p);
      if (d <= 0) {
        poly1.addPoint(p);
      }
      if (d >= 0 && poly2) {
        poly2.addPoint(this.flipPointHorizontally(p));
      }
    }
  
    /**
     * Sets the options for the effect, merging in defaults.
     * @param {Object} opt User options.
     * @private
     */
    Peel.prototype.setOptions = function(opt) {
      var options = opt || {}, defaults = Peel.Defaults;
      for (var key in defaults) {
        if (!defaults.hasOwnProperty(key) || key in options) {
          continue;
        }
        options[key] = defaults[key];
      }
      this.options = options;
    }
  
    /**
     * Finds or creates a layer in the dom.
     * @param {string} id The internal id of the element to be found or created.
     * @param {HTMLElement} parent The parent if the element needs to be created.
     * @param {numer} zIndex The z index of the layer.
     * @returns {HTMLElement}
     * @private
     */
    Peel.prototype.findOrCreateLayer = function(id, parent, zIndex) {
      var optId = id + '-element';
      var domId = prefix(id);
      var el = getElement(this.getOption(optId) || '.' + domId, parent);
      if (!el) {
        el = createElement(parent, domId);
      }
      addClass(el, prefix('layer'));
      setZIndex(el, zIndex);
      return el;
    }
  
    /**
     * Returns either a point created from 2 arguments (x/y) or a corner point
     * created from the first argument as a corner id.
     * @param {Arguments} args The arguments object from the original function.
     * @returns {Point}
     * @private
     */
    Peel.prototype.getPointOrCorner = function(args) {
      if (args.length === 2) {
        return new Point(args[0], args[1]);
      } else if(typeof args[0] === 'number') {
        return this.getCornerPoint(args[0]);
      }
      return args[0];
    }
  
    /**
     * Returns a corner point based on an id defined in Peel.Corners.
     * @param {number} id The id of the corner.
     * @private
     */
    Peel.prototype.getCornerPoint = function(id) {
      var x = +!!(id & 1) * this.width;
      var y = +!!(id & 2) * this.height;
      return new Point(x, y);
    }
  
    /**
     * Gets an optional clipping shape that may be set by the user.
     * @returns {Object}
     * @private
     */
    Peel.prototype.getOptionalShape = function() {
      var shapes = ['rect', 'polygon', 'path', 'circle'], found;
      shapes.some(function(type) {
        var attr = this.getOption(type), obj;
        if (attr) {
          obj = {};
          obj.attributes = attr;
          obj.type = type;
          found = obj;
        }
        return found;
      }, this);
      return found;
    }
  
    /**
     * Sets up the main layers used for the effect that may include a possible
     * subclip shape.
     * @private
     */
    Peel.prototype.setupLayers = function() {
      var shape = this.getOptionalShape();
  
      // The inner layers may be wrapped later, so keep a reference to them here.
      var topInnerLayer  = this.topLayer  = this.findOrCreateLayer('top', this.el, 2);
      var backInnerLayer = this.backLayer = this.findOrCreateLayer('back', this.el, 3);
  
      this.bottomLayer = this.findOrCreateLayer('bottom', this.el, 1);
  
      if (shape) {
        // If there is an SVG shape specified in the options, then this needs to
        // be a separate clipped element because Safari/Mobile Safari can't handle
        // nested clip-paths. The current top/back element will become the shape
        // clip, so wrap them with an "outer" clip element that will become the
        // new layer for the peel effect. The bottom layer does not require this
        // effect, so the shape clip can be set directly on it.
        this.topLayer  = this.wrapShapeLayer(this.topLayer, 'top-outer-clip');
        this.backLayer = this.wrapShapeLayer(this.backLayer, 'back-outer-clip');
  
        this.topShapeClip    = new SVGClip(topInnerLayer, shape);
        this.backShapeClip   = new SVGClip(backInnerLayer, shape);
        this.bottomShapeClip = new SVGClip(this.bottomLayer, shape);
  
        if (this.getOption('topShadowCreatesShape')) {
          this.topShadowElement = this.setupDropShadow(shape, topInnerLayer);
        }
      } else {
        this.topShadowElement = this.findOrCreateLayer('top-shadow', topInnerLayer, 1);
      }
  
      this.topClip = new SVGClip(this.topLayer);
      this.backClip = new SVGClip(this.backLayer);
  
      this.backShadowElement     = this.findOrCreateLayer('back-shadow', backInnerLayer, 1);
      this.backReflectionElement = this.findOrCreateLayer('back-reflection', backInnerLayer, 2);
      this.bottomShadowElement   = this.findOrCreateLayer('bottom-shadow', this.bottomLayer, 1);
  
      this.usesBoxShadow = !shape;
    }
  
    /**
     * Creates an inline SVG element to be used as a layer for a drop shadow filter
     * effect. Note that drop shadow filters currently have some odd quirks in
     * Blink such as blur radius changing depending on rotation, etc.
     * @param {Object} shape A shape describing the SVG element to be used.
     * @param {HTMLElement} parent The parent element where the layer will be added.
     * @returns {SVGElement}
     * @private
     */
    Peel.prototype.setupDropShadow = function(shape, parent) {
      var svg = createSVGElement('svg', parent, {
        'class': prefix('layer')
      });
      createSVGElement(shape.type, svg, shape.attributes);
      return svg;
    }
  
    /**
     * Wraps the passed element in another layer, preserving its z-index. Also
     * add a "shape-layer" class to the layer which now becomes a shape clip.
     * @param {HTMLElement} el The element to become the wrapped shape layer.
     * @param {string} id The identifier for the new layer that will wrap the element.
     * @returns {HTMLElement} The new element that wraps the shape layer.
     * @private
     */
    Peel.prototype.wrapShapeLayer = function(el, id) {
      var zIndex = getZIndex(el);
      addClass(el, prefix('shape-layer'));
      var outerLayer = this.findOrCreateLayer(id, this.el, zIndex);
      outerLayer.appendChild(el);
      return outerLayer;
    }
  
    /**
     * Sets up the dimensions of the element box and clipping box that area used
     * in the effect.
     * @private
     */
    Peel.prototype.setupDimensions = function() {
      this.width  = this.el.offsetWidth;
      this.height = this.el.offsetHeight;
      this.center = new Point(this.width / 2, this.height / 2);
  
      this.elementBox  = this.getScaledBox(1);
      this.clippingBox = this.getScaledBox(this.getOption('clippingBoxScale'));
    }
  
    /**
     * Gets a box defined by 4 line segments that is at a scale of the main
     * element.
     * @param {number} scale The scale for the box to be.
     * @private
     */
    Peel.prototype.getScaledBox = function(scale) {
  
      // Box scale is equal to:
      // 1 * the bottom/right scale
      // 0 * the top/left scale.
      var brScale = scale;
      var tlScale = scale - 1;
  
      var tl = new Point(-this.width * tlScale, -this.height * tlScale);
      var tr = new Point( this.width * brScale, -this.height * tlScale);
      var br = new Point( this.width * brScale,  this.height * brScale);
      var bl = new Point(-this.width * tlScale,  this.height * brScale);
  
      return [
        new LineSegment(tl, tr),
        new LineSegment(tr, br),
        new LineSegment(br, bl),
        new LineSegment(bl, tl)
      ];
    }
  
    /**
     * Returns the peel position adjusted by constraints, if there are any.
     * @param {Point} point The peel position to be constrained.
     * @returns {Point}
     * @private
     */
    Peel.prototype.getConstrainedPeelPosition = function(pos) {
      this.constraints.forEach(function(area) {
        var offset = this.getFlipConstraintOffset(area, pos);
        if (offset) {
          area = new Circle(area.center, area.radius - offset);
        }
        pos = area.constrainPoint(pos);
      }, this);
      return pos;
    }
  
    /**
     * Returns an offset to "pull" a corner in to prevent the peel effect from
     * suddenly flipping around its axis. This offset is intended to be applied
     * on the Y axis when dragging away from the center.
     * @param {Circle} area The constraint to check against.
     * @param {Point} point The peel position to be constrained.
     * @returns {number|undefined}
     * @private
     */
    Peel.prototype.getFlipConstraintOffset = function(area, pos) {
      var offset = this.getOption('flipConstraintOffset');
      if (area === this.flipConstraint && offset) {
        var cornerToCenter = this.corner.subtract(this.center);
        var cornerToConstraint = this.corner.subtract(area.center);
        var baseAngle = cornerToConstraint.getAngle();
  
        // Normalized angles are rotated to be in the same space relative
        // to the constraint.
        var nCornerToConstraint = cornerToConstraint.rotate(-baseAngle);
        var nPosToConstraint = pos.subtract(area.center).rotate(-baseAngle);
  
        // Flip the vector vertically if the corner is in the bottom left or top
        // right relative to the center, as the effect should always pull away
        // from the vertical midline.
        if (cornerToCenter.x * cornerToCenter.y < 0) {
          nPosToConstraint.y *= -1;
        }
  
        if (nPosToConstraint.x > 0 && nPosToConstraint.y > 0) {
          return normalize(nPosToConstraint.getAngle(), 45, 0) * offset;
        }
  
      }
    }
  
    /**
     * Gets the line segment that represents the current peel line.
     * @param {Point} point The position of the peel corner.
     * @returns {LineSegment}
     * @private
     */
    Peel.prototype.getPeelLineSegment = function(point) {
      // The point midway between the peel position and the corner.
      var halfToCorner = this.corner.subtract(point).scale(.5);
      var midpoint = point.add(halfToCorner);
      if (halfToCorner.x === 0 && halfToCorner.y === 0) {
        // If the corner is the same as the point, then set half to corner
        // to be the center, and keep the midpoint where it is. This will
        // ensure a non-zero peel line.
        halfToCorner = point.subtract(this.center);
      }
      var l = halfToCorner.getLength()
      var mult = (Math.max(this.width, this.height) / l) * 10;
      var half = halfToCorner.rotate(-90).scale(mult);
      var p1 = midpoint.add(half);
      var p2 = midpoint.subtract(half);
      return new LineSegment(p1, p2);
    }
  
    /**
     * Sets the transform of the back layer.
     * @param {Point} pos The position of the peeling corner.
     * @private
     */
    Peel.prototype.setBackTransform = function(pos) {
      var mirroredCorner = this.flipPointHorizontally(this.corner);
      var r = (this.peelLineRotation - 90) * 2;
      var t = pos.subtract(mirroredCorner.rotate(r));
      var css = 'translate('+ round(t.x) +'px, '+ round(t.y) +'px) rotate('+ round(r) +'deg)';
      setTransform(this.backLayer, css);
  
      // Set the top shadow element here as well, as the
      // position and rotation matches that of the back layer.
      setTransform(this.topShadowElement, css);
    }
  
    /**
     * Gets the distance of the peel line along an imaginary line that runs
     * between the corners that it "faces". For example, if the peel line
     * is rotated 45 degrees, then it can be considered to be between the top left
     * and bottom right corners. This function will return how far the peel line
     * has advanced along that line.
     * @returns {number} A position >= 0.
     * @private
     */
    Peel.prototype.getPeelLineDistance = function() {
      var cornerId, opposingCornerId, corner, opposingCorner;
      if (this.peelLineRotation < 90) {
        cornerId = Peel.Corners.TOP_RIGHT;
        opposingCornerId = Peel.Corners.BOTTOM_LEFT;
      } else if (this.peelLineRotation < 180) {
        cornerId = Peel.Corners.BOTTOM_RIGHT;
        opposingCornerId = Peel.Corners.TOP_LEFT;
      } else if (this.peelLineRotation < 270) {
        cornerId = Peel.Corners.BOTTOM_LEFT;
        opposingCornerId = Peel.Corners.TOP_RIGHT;
      } else if (this.peelLineRotation < 360) {
        cornerId = Peel.Corners.TOP_LEFT;
        opposingCornerId = Peel.Corners.BOTTOM_RIGHT;
      }
      corner = this.getCornerPoint(cornerId);
      opposingCorner = this.getCornerPoint(opposingCornerId);
  
      // Scale the line segment past the original corners so that the effects
      // can have a nice fadeout even past 1.
      var cornerToCorner = new LineSegment(corner, opposingCorner).scale(2);
      var intersect = this.peelLineSegment.getIntersectPoint(cornerToCorner);
      if (!intersect) {
        // If there is no intersect, then assume that it has run past the opposing
        // corner and set the distance to well past the full distance.
        return 2;
      }
      var distanceToPeelLine = corner.subtract(intersect).getLength();
      var totalDistance      = corner.subtract(opposingCorner).getLength();
      return (distanceToPeelLine / totalDistance);
    }
  
    /**
     * Sets shadows and fade effects.
     * @private
     */
    Peel.prototype.setEffects = function() {
      var t = this.getPeelLineDistance();
      this.setTopShadow(t);
      this.setBackShadow(t);
      this.setBackReflection(t);
      this.setBottomShadow(t);
      this.setFade();
    }
  
    /**
     * Sets the top shadow as either a box-shadow or a drop-shadow filter.
     * @param {number} t Position of the peel line from corner to corner.
     * @private
     */
    Peel.prototype.setTopShadow = function(t) {
      if (!this.getOption('topShadow')) {
        return;
      }
      var sBlur  = this.getOption('topShadowBlur');
      var sX     = this.getOption('topShadowOffsetX');
      var sY     = this.getOption('topShadowOffsetY');
      var alpha  = this.getOption('topShadowAlpha');
      var sAlpha = this.exponential(t, 5, alpha);
      if (this.usesBoxShadow) {
        setBoxShadow(this.topShadowElement, sX, sY, sBlur, 0, sAlpha);
      } else {
        setDropShadow(this.topShadowElement, sX, sY, sBlur, sAlpha);
      }
    }
  
    /**
     * Gets a number either distributed along a bell curve or increasing linearly.
     * @param {number} n The number to transform.
     * @param {boolean} dist Whether or not to use distribution.
     * @param {number} mult A multiplier for the result.
     * @returns {number}
     * @private
     */
    Peel.prototype.distributeOrLinear = function(n, dist, mult) {
      if (dist) {
        return distribute(n, mult);
      } else {
        return n * mult;
      }
    }
  
    /**
     * Gets a number either distributed exponentially, clamped to a range between
     * 0 and 1, and multiplied by a multiplier.
     * @param {number} n The number to transform.
     * @param {number} exp The exponent to be used.
     * @param {number} mult A multiplier for the result.
     * @returns {number}
     * @private
     */
    Peel.prototype.exponential = function(n, exp, mult) {
      return mult * clamp(Math.pow(1 + n, exp) - 1);
    }
  
    /**
     * Sets reflection of the back face as a linear gradient.
     * @param {number} t Position of the peel line from corner to corner.
     * @private
     */
    Peel.prototype.setBackReflection = function(t) {
      var stops = [];
      if (this.canSetLinearEffect('backReflection', t)) {
  
        var rDistribute = this.getOption('backReflectionDistribute');
        var rSize = this.getOption('backReflectionSize');
        var rOffset = this.getOption('backReflectionOffset');
        var rAlpha = this.getOption('backReflectionAlpha');
  
        var reflectionSize = this.distributeOrLinear(t, rDistribute, rSize);
        var rStop  = t - rOffset;
        var rMid   = rStop - reflectionSize;
        var rStart = rMid - reflectionSize;
  
        stops.push(getWhiteStop(0, 0));
        stops.push(getWhiteStop(0, rStart));
        stops.push(getWhiteStop(rAlpha, rMid));
        stops.push(getWhiteStop(0, rStop));
      }
      setBackgroundGradient(this.backReflectionElement, 180 - this.peelLineRotation, stops);
    }
  
    /**
     * Sets shadow of the back face as a linear gradient.
     * @param {number} t Position of the peel line from corner to corner.
     * @private
     */
    Peel.prototype.setBackShadow = function(t) {
      var stops = [];
      if (this.canSetLinearEffect('backShadow', t)) {
  
        var sSize       = this.getOption('backShadowSize');
        var sOffset     = this.getOption('backShadowOffset');
        var sAlpha      = this.getOption('backShadowAlpha');
        var sDistribute = this.getOption('backShadowDistribute');
  
        var shadowSize  = this.distributeOrLinear(t, sDistribute, sSize);
        var shadowStop  = t - sOffset;
        var shadowMid   = shadowStop - shadowSize;
        var shadowStart = shadowMid - shadowSize;
  
        stops.push(getBlackStop(0, 0));
        stops.push(getBlackStop(0, shadowStart));
        stops.push(getBlackStop(sAlpha, shadowMid));
        stops.push(getBlackStop(sAlpha, shadowStop));
      }
      setBackgroundGradient(this.backShadowElement, 180 - this.peelLineRotation, stops);
    }
  
    /**
     * Sets the bottom shadow as a linear gradient.
     * @param {number} t Position of the peel line from corner to corner.
     * @private
     */
    Peel.prototype.setBottomShadow = function(t) {
      var stops = [];
      if (this.canSetLinearEffect('bottomShadow', t)) {
  
        // Options
        var sSize = this.getOption('bottomShadowSize');
        var offset = this.getOption('bottomShadowOffset');
        var darkAlpha = this.getOption('bottomShadowDarkAlpha');
        var lightAlpha = this.getOption('bottomShadowLightAlpha');
        var sDistribute = this.getOption('bottomShadowDistribute');
  
        var darkShadowStart = t - (.025 - offset);
        var midShadowStart = darkShadowStart - (this.distributeOrLinear(t, sDistribute, .03) * sSize) - offset;
        var lightShadowStart = midShadowStart - ((.02 * sSize) - offset);
        stops = [
          getBlackStop(0, 0),
          getBlackStop(0, lightShadowStart),
          getBlackStop(lightAlpha, midShadowStart),
          getBlackStop(lightAlpha, darkShadowStart),
          getBlackStop(darkAlpha, t)
        ];
      }
      setBackgroundGradient(this.bottomShadowElement, this.peelLineRotation + 180, stops);
    }
  
    /**
     * Whether a linear effect can be set.
     * @param {string} name Name of the effect
     * @param {number} t Current position of the linear effect line.
     * @returns {boolean}
     * @private
     */
    Peel.prototype.canSetLinearEffect = function(name, t) {
      return this.getOption(name) && t > 0;
    }
  
    /**
     * Sets the fading effect of the top layer, if a threshold is set.
     * @private
     */
    Peel.prototype.setFade = function() {
      var threshold = this.fadeThreshold, opacity = 1, n;
      if (threshold) {
        if (this.timeAlongPath !== undefined) {
          n = this.timeAlongPath;
        } else {
          n = this.getAmountClipped();
        }
        if (n > threshold) {
          opacity = (1 - n) / (1 - threshold);
        }
        setOpacity(this.topLayer, opacity);
        setOpacity(this.backLayer, opacity);
        setOpacity(this.bottomShadowElement, opacity);
      }
    }
  
    /**
     * Flips a point along an imaginary vertical midpoint.
     * @param {Array} points The points to be flipped.
     * @returns {Array}
     * @private
     */
    Peel.prototype.flipPointHorizontally = function(p) {
      return new Point(p.x - ((p.x - this.center.x) * 2), p.y);
    }
  
    /**
     * Post setup initialization.
     * @private
     */
    Peel.prototype.init = function() {
      if (this.getOption('setPeelOnInit')) {
        this.setPeelPosition(this.corner);
      }
      addClass(this.el, prefix('ready'));
    }
  
    /**
     * Class that clips an HTMLElement by an SVG path.
     * @param {HTMLElement} el The element to be clipped.
     * @param {Object} [shape] An object defining the SVG element to use in the new
     *     clip path. Defaults to a polygon.
     * @constructor
     */
    function SVGClip (el, shape) {
      this.el = el;
      this.shape = SVGClip.createClipPath(el, shape || {
        'type': 'polygon'
      });
      // Chrome needs this for some reason for the clipping to work.
      setTransform(this.el, 'translate(0px,0px)');
    }
  
    /**
     * Sets up the global SVG element and its nested defs object to use for new
     * clip paths.
     * @returns {SVGElement}
     * @public
     */
    SVGClip.getDefs = function() {
      if (!this.defs) {
        this.svg  = createSVGElement('svg', null, {
          'class': prefix('svg-clip-element')
        });
        this.defs = createSVGElement('defs', this.svg);
      }
      return this.defs;
    }
  
    /**
     * Creates a new <clipPath> SVG element and sets the passed html element to be
     * clipped by it.
     * @param {HTMLElement} el The html element to be clipped.
     * @param {Object} obj An object defining the SVG element to be used in the
     *     clip path.
     * @returns {SVGElement}
     * @public
     */
    SVGClip.createClipPath = function(el, obj) {
      var id = SVGClip.getId();
      var clipPath = createSVGElement('clipPath', this.getDefs());
      var svgEl = createSVGElement(obj.type, clipPath, obj.attributes);
      setSVGAttribute(clipPath, 'id', id);
      setCSSClip(el, 'url(#' + id + ')');
      return svgEl;
    }
  
    /**
     * Gets the next svg clipping id.
     * @public
     */
    SVGClip.getId = function() {
      if (!SVGClip.id) {
        SVGClip.id = 1;
      }
      return 'svg-clip-' + SVGClip.id++;
    }
  
    /**
     * Sets the "points" attribute of the clip path shape. This only makes sense
     * for polygon shapes.
     * @param {Array} points The points to be used.
     * @public
     */
    SVGClip.prototype.setPoints = function(points) {
      var str = points.map(function(p) {
        return round(p.x) + ',' + round(p.y);
      }).join(' ');
      setSVGAttribute(this.shape, 'points', str);
    }
  
    /**
     * A class that represents a circle.
     * @param {Point} center The center point.
     * @param {Point} radius The radius.
     * @constructor
     */
    function Circle (center, radius) {
      this.center = center;
      this.radius = radius;
    }
  
    /**
     * Determines whether a point is contained within the circle.
     * @param {Point} p The point.
     * @returns {boolean}
     * @public
     */
    Circle.prototype.containsPoint = function(p) {
      if(this.boundingRectContainsPoint(p)) {
          var dx = this.center.x - p.x;
          var dy = this.center.y - p.y;
          dx *= dx;
          dy *= dy;
          var distanceSquared = dx + dy;
          var radiusSquared = this.radius * this.radius;
          return distanceSquared <= radiusSquared;
      }
      return false;
    }
  
    /**
     * Determines whether a point is contained within the bounding box of the circle.
     * @param {Point} p The point.
     * @returns {boolean}
     * @private
     */
    Circle.prototype.boundingRectContainsPoint = function(p) {
      return p.x >= this.center.x - this.radius && p.x <= this.center.x + this.radius &&
             p.y >= this.center.y - this.radius && p.y <= this.center.y + this.radius;
    }
  
    /**
     * Moves a point outside the circle to the closest point on the circumference.
     * Rotated angle from the center point should be the same.
     * @param {Point} p The point.
     * @returns {boolean}
     * @public
     */
    Circle.prototype.constrainPoint = function(p) {
      if (!this.containsPoint(p)) {
        var rotation = p.subtract(this.center).getAngle();
        p = this.center.add(new Point(this.radius, 0).rotate(rotation));
      }
      return p;
    }
  
    /**
     * A class that represents a polygon.
     * @constructor
     */
    function Polygon() {
      this.points = [];
    }
  
    /**
     * Gets the area of the polygon.
     * @param {Array} points The points describing the polygon.
     * @public
     */
    Polygon.getArea = function(points) {
      var sum1 = 0, sum2 = 0;
      points.forEach(function(p, i, arr) {
        var next = arr[(i + 1) % arr.length];
        sum1 += (p.x * next.y);
        sum2 += (p.y * next.x);
      });
      return (sum1 - sum2) / 2;
    }
  
    /**
     * Adds a point to the polygon.
     * @param {Point} point
     * @public
     */
    Polygon.prototype.addPoint = function(point) {
      this.points.push(point);
    }
  
    /**
     * Gets the points of the polygon as an array.
     * @returns {Array}
     * @public
     */
    Polygon.prototype.getPoints = function() {
      return this.points;
    }
  
  
    /**
     * A class representing a bezier curve.
     * @param {Point} p1 The starting point.
     * @param {Point} c1 The control point of p1.
     * @param {Point} c2 The control point of p2.
     * @param {Point} p2 The ending point.
     * @constructor
     */
    function BezierCurve (p1, c1, c2, p2) {
      this.p1 = p1;
      this.c1 = c1;
      this.p2 = p2;
      this.c2 = c2;
    }
  
    /**
     * Gets a point along the line segment for a given time.
     * @param {number} t The time along the segment, between 0 and 1.
     * @returns {Point}
     */
    BezierCurve.prototype.getPointForTime = function(t) {
      var b0 = Math.pow(1 - t, 3);
      var b1 = 3 * t * Math.pow(1 - t, 2);
      var b2 = 3 * Math.pow(t, 2) * (1 - t);
      var b3 = Math.pow(t, 3);
  
      var x = (b0 * this.p1.x) + (b1 * this.c1.x) + (b2 * this.c2.x) + (b3 * this.p2.x)
      var y = (b0 * this.p1.y) + (b1 * this.c1.y) + (b2 * this.c2.y) + (b3 * this.p2.y)
      return new Point(x, y);
    }
  
  
    /**
     * A class that represents a line segment.
     * @param {Point} p1 The start of the segment.
     * @param {Point} p2 The end of the segment.
     * @constructor
     */
    function LineSegment (p1, p2) {
      this.p1 = p1;
      this.p2 = p2;
    }
  
    /**
     * @constant
     */
    LineSegment.EPSILON = 1e-6;
  
    /**
     * Gets a point along the line segment for a given time.
     * @param {number} t The time along the segment, between 0 and 1.
     * @returns {Point}
     * @public
     */
    LineSegment.prototype.getPointForTime = function(t) {
      return this.p1.add(this.getVector().scale(t));
    }
  
    /**
     * Takes a scalar and returns a new scaled line segment.
     * @param {number} n The amount to scale the segment by.
     * @returns {LineSegment}
     * @public
     */
    LineSegment.prototype.scale = function(n) {
      var half = 1 + (n / 2);
      var p1 = this.p1.add(this.p2.subtract(this.p1).scale(n));
      var p2 = this.p2.add(this.p1.subtract(this.p2).scale(n));
      return new LineSegment(p1, p2);
    }
  
    /**
     * The determinant is a number that indicates which side of a line a point
     * falls on. A positive number means that the point falls inside the area
     * "clockwise" of the line, ie. the area that the line would sweep if it were
     * rotated 180 degrees. A negative number would mean the point is in the area
     * the line would sweep if it were rotated counter-clockwise, or -180 degrees.
     * 0 indicates that the point falls exactly on the line.
     * @param {Point} p The point to test against.
     * @returns {number} A signed number.
     * @public
     */
    LineSegment.prototype.getPointDeterminant = function(p) {
      var d = ((p.x - this.p1.x) * (this.p2.y - this.p1.y)) - ((p.y - this.p1.y) * (this.p2.x - this.p1.x));
      // Tolerance for near-zero.
      if (d > -LineSegment.EPSILON && d < LineSegment.EPSILON) {
        d = 0;
      }
      return d;
    }
  
    /**
     * Calculates the point at which another line segment intersects, if any.
     * @param {LineSegment} seg The second line segment.
     * @returns {Point|null}
     * @public
     */
    LineSegment.prototype.getIntersectPoint = function(seg2) {
      var seg1 = this;
  
      function crossProduct(p1, p2) {
        return p1.x * p2.y - p1.y * p2.x;
      }
  
      var r = seg1.p2.subtract(seg1.p1);
      var s = seg2.p2.subtract(seg2.p1);
  
      var uNumerator = crossProduct(seg2.p1.subtract(seg1.p1), r);
      var denominator = crossProduct(r, s);
  
      if (denominator == 0) {
        // ignoring colinear and parallel
        return null;
      }
  
      var u = uNumerator / denominator;
      var t = crossProduct(seg2.p1.subtract(seg1.p1), s) / denominator;
  
      if ((t >= 0) && (t <= 1) && (u >= 0) && (u <= 1)) {
        return seg1.p1.add(r.scale(t));
      }
  
      return null;
    }
  
    /**
     * Returns the angle of the line segment in degrees.
     * @returns {number}
     * @public
     */
    LineSegment.prototype.getAngle = function() {
      return this.getVector().getAngle();
    }
  
    /**
     * Gets the vector that represents the line segment.
     * @returns {Point}
     * @private
     */
    LineSegment.prototype.getVector = function() {
      if (!this.vector) {
        this.vector = this.p2.subtract(this.p1);
      }
      return this.vector;
    }
  
    /**
     * A class representing a point or 2D vector.
     * @param {number} x The x coordinate.
     * @param {number} y The y coordinate.
     * @constructor
     */
    function Point (x, y) {
      this.x = x;
      this.y = y;
    }
  
    /**
     * @constant
     */
    Point.DEGREES_IN_RADIANS = 180 / Math.PI;
  
    /**
     * Gets degrees in radians.
     * @param {number} deg
     * @returns {number}
     */
    Point.degToRad = function(deg) {
      return deg / Point.DEGREES_IN_RADIANS;
    };
  
    /**
     * Gets radians in degrees.
     * @param {number} rad
     * @returns {number}
     */
    Point.radToDeg = function(rad) {
      var deg = rad * Point.DEGREES_IN_RADIANS;
      while(deg < 0) deg += 360;
      return deg;
    };
  
    /**
     * Creates a new point given a rotation in degrees and a length.
     * @param {number} deg The rotation of the vector.
     * @param {number} len The length of the vector.
     * @returns {Point}
     */
    Point.vector = function(deg, len) {
      var rad = Point.degToRad(deg);
      return new Point(Math.cos(rad) * len, Math.sin(rad) * len);
    };
  
    /**
     * Adds a point.
     * @param {Point} p
     * @returns {Point}
     */
    Point.prototype.add = function(p) {
      return new Point(this.x + p.x, this.y + p.y);
    };
  
    /**
     * Subtracts a point.
     * @param {Point} p
     * @returns {Point}
     */
    Point.prototype.subtract = function(p) {
      return new Point(this.x - p.x, this.y - p.y);
    };
  
    /**
     * Scales a point by a scalar.
     * @param {number} n
     * @returns {Point}
     */
    Point.prototype.scale = function(n) {
      return new Point(this.x * n, this.y * n);
    };
  
    /**
     * Gets the length of the distance to the point.
     * @returns {number}
     */
    Point.prototype.getLength = function() {
      return Math.sqrt(Math.pow(this.x, 2) + Math.pow(this.y, 2));
    };
  
    /**
     * Gets the angle of the point in degrees.
     * @returns {number}
     */
    Point.prototype.getAngle = function() {
      return Point.radToDeg(Math.atan2(this.y, this.x));
    };
  
    /**
     * Returns a new point of the same length with a different angle.
     * @param {number} deg The angle in degrees.
     * @returns {Point}
     */
    Point.prototype.setAngle = function(deg) {
      return Point.vector(deg, this.getLength());
    };
  
    /**
     * Rotates the point.
     * @param {number} deg The amount to rotate by in degrees.
     * @returns {Point}
     */
    Point.prototype.rotate = function(deg) {
      return this.setAngle(this.getAngle() + deg);
    };
  
    setCssProperties();
    win.Peel = Peel;
  
  })(window);
  