window.requestAnimFrame = (function(){
    return  window.requestAnimationFrame       ||
            window.webkitRequestAnimationFrame ||
            window.mozRequestAnimationFrame    ||
            window.oRequestAnimationFrame      ||
            window.msRequestAnimationFrame     ||
            function(/* function */ callback, /* DOMElement */ element){
              window.setTimeout(callback, 1000 / 60);
            };
  })();