Run(){
            if(this._timerID > -1){
                return;
            }
            let scope = this;
            let thisTimerId = -1;
            let time = 1000 / (this._fps);
            this._gameClock.Start();
            let step = (timestamp)=>{
                if(thisTimerId !== scope._timerID){
                    return;
                }
                let ms = this._gameClock.ElapsedMilliseconds;
                if(ms >= time){
                    this.Update();
                    this.Draw();
                    this._gameClock.Restart();
                    let newEs = (ms % time);
                    this._gameClock._elapsedTime = newEs;
                }
                window.requestAnimationFrame(step);
            };
            this._timerID = window.requestAnimationFrame(step);
            thisTimerId = this._timerID;
        }