//requestAnimationFrame polyfill
(function () {
    "use strict";

    var lastTime = 0;
    var vendors  = ['webkit', 'moz'];

    for (var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
        window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame'];
        window.cancelAnimationFrame  = window[vendors[x] + 'CancelAnimationFrame'] ||
                                       window[vendors[x] + 'CancelRequestAnimationFrame'];
    }

    if (!window.requestAnimationFrame) {
        window.requestAnimationFrame = function (callback) {
            var currTime   = new Date().getTime();
            var timeToCall = Math.max(0, 16 - (currTime - lastTime));

            var id = window.setTimeout(function () {
                callback(currTime + timeToCall);
            }, timeToCall);

            lastTime = currTime + timeToCall;

            return id;
        };
    }

    if (!window.cancelAnimationFrame) {
        window.cancelAnimationFrame = function (id) {
            clearTimeout(id);
        };
    }
}());
