1. 通过Code初始化View及Scene的方法

override func viewDidLoad() {
        super.viewDidLoad()
        
        //Initialize scene
        let scene = GameScene(size: CGSize(width: 1920, height: 1080))
        
        //Initialize skView
        let skView = self.view as! SKView
        
        //Set FPS & node count present in the scene
        skView.showsFPS = true
        
        skView.showsNodeCount = true
        
        //A Boolean value that indicates whether parent-child and sibling relationships affect the rendering order of nodes in the scene.
        skView.ignoresSiblingOrder = true
        
        //Set the scaleMode
        scene.scaleMode = .aspectFill
        
        //Present scene in skView
        skView.presentScene(scene)
       
        
    }

2. Sprite在scene中不考虑其他因素的自然移动，需在update()方法中添加：

zombie.position =  CGPoint(x: zombie.position.x+1, y: zombie.position.y)