code: function update(dt) {
           var duration = 0,
               now = me.timer.getTime(),
               result = false;
  
           if (this._lastUpdate !== now) {
             this._lastUpdate = now;
             this.animations.forEach(function (anim) {
               anim.dt += dt;
               duration = anim.cur.duration;
  
               while (anim.dt >= duration) {
                 anim.dt -= duration;
                 anim.idx = (anim.idx + 1) % anim.frames.length;
                 anim.cur = anim.frames[anim.idx];
                 duration = anim.cur.duration;
                 result = true;
               }
             });
           }
  
           return result;
         }
docs: update tile animations