public void StartScreen()
        {
            startScreen   = new StartScreen(this);
            currentScreen = Screen.StartScreen;

            gameSelectScreen = null;
            gameOverScreen   = null;
            gamePlayScreen   = null;
        }
        public void SelectScreen()
        {
            gameSelectScreen = new GameSelectScreen(this);
            currentScreen    = Screen.GameSelectScreen;

            startScreen    = null;
            gameOverScreen = null;
            gamePlayScreen = null;
        }