text: // Copyright 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  var sprites = (function() {
    var objs;
    var width;
    var height;
    var SPRITE_SPEED = 2;
  
    var sprites = {};
    sprites.init = function(w, h) {
      objs = [];
      width = w;
      height = h;
    };
    sprites.add = function(img) {
      var obj = { img: img,
                    x: Math.random() * (width - img.width),
                    y: Math.random() * (height - img.height),
                   dx: SPRITE_SPEED * (Math.random() < .5 ? -1 : 1),
                   dy: SPRITE_SPEED * (Math.random() < .5 ? -1 : 1) };
      objs.push(obj);
    };
    sprites.draw = function(context) {
      for (var i = 0, len = objs.length; i < len; ++i) {
        var obj = objs[i];
  
        obj.x += obj.dx;
        if ((obj.x > (width - obj.img.width)) || (obj.x < 0))
          obj.dx *= -1;
  
        obj.y += obj.dy;
        if ((obj.y > (height - obj.img.height)) || (obj.y < 0))
          obj.dy *= -1;
  
        context.drawImage(obj.img, obj.x, obj.y);
    };
    };
    return sprites;
  })();
  