SwiftのSpriteKitで実装―タワーディフェンスゲームの大枠の作り方とコツ：iOS SDKとSwiftで始めるゲーム作成入門（2）（2/3 ページ）

class GameScene: SKScene {
    let enemy = SKSpriteNode(imageNamed: "Enemy")
    
    override func didMoveToView(view: SKView) {
        // …略
        
        enemy.position = CGPoint(x:50, y:300)
        addChild(enemy)
    }
}

override func update(currentTime: NSTimeInterval) {
    enemy.position.x += 1
}

class GameScene: SKScene {
    enum State {
        case Playing
        case GameClear
        case GameOver
    }
    var state = State.Playing
    
    // ...略
}

class GameScene: SKScene {
// ...略
 
    override func update(currentTime: NSTimeInterval) {
        if state == .Playing {
            enemy.position.x += 1
            
            if frame.width < enemy.position.x {
                state = .GameOver
                
                let myLabel = SKLabelNode(fontNamed: "HiraginoSans-W6")
                myLabel.text = "ゲームオーバー"
                myLabel.fontSize = 45
                myLabel.position = CGPoint(x:CGRectGetMidX(self.frame), y:CGRectGetMidY(self.frame) - 20)
                addChild(myLabel)
            }
        }
    }
}