public void ChangeScreen(string newScreen)
        {
            // UnLoad();
            currentScreen = null;
            switch (newScreen)
            {
            case "StartScreen":
                currentScreen = startScreen;     //new StartScreen();
                break;

            case "MainGameScreen":
                if (gameScreen == null)
                {
                    gameScreen = new MainGameScreen();
                }
                currentScreen = gameScreen;    //new MainGameScreen();

                break;

            case "Exit": exitGame = true;
                return;
            }
            GC.Collect();
            currentScreen.Init();
            currentScreen.Load();
        }
 public GameManager()
 {
     //GameScreen
     //currentScreen = new MainGameScreen();
     //StartScreen
     startScreen   = new StartScreen();
     currentScreen = startScreen;
 }