app.stage.addChild(bg);

    var speedList = [];//小车速度列表
    var carList = [];//小车列表

    for(var i=0;i<5;i++){
    var car = new PIXI.Sprite.fromImage(“res/racer/saiche-7_03.png”);
    car.anchor.set(0.5,0.5);
    car.x = 200 + i30;
    car.y = 650;
    app.stage.addChild(car);
    carList.push(car);
    speedList.push(Math.random()    (7-2)+2);
    }

    app.ticker.add(animate);
    function animate(){
    moveBg()
    moveCar();
    }

    //移动背景
    function moveBg(){
    bg.y += 1;
    if(bg.y > 0){
    bg.y = -600;
    }
    }
    //移动小车
    function moveCar(){
    for(var i=0;i<5;i++){
    carList[i].y-=speedList[i];
    if(carList[i].y<-50){
    carList[i].y=650;
    speedList[i] = Math.random()*(7-2)+2;
    }
    }
    }