protected override void Update(GameTime gameTime)
    {
        switch (screen.State)
        {
            case ScreenManager.ScreenState.MENU:
                screen.Update();
                break;
            case ScreenManager.ScreenState.OPTIONS:
                screen.Update();
                break;
            case ScreenManager.ScreenState.PLAY:
                UpdateGame(gameTime);
                break;
            case ScreenManager.ScreenState.EXIT:
                this.Exit();
                break;
        }

        Console.WriteLine(screen.State);
        base.Update(gameTime);
    }

public void Update()
    {
        switch (screenState)
        {
            case ScreenState.MENU:
                if (keyState.IsKeyDown(Keys.Space) && lastKeyState.IsKeyUp(Keys.Space))
                    screenState = ScreenState.OPTIONS;
                break;
            case ScreenState.OPTIONS:
                if (keyState.IsKeyDown(Keys.Space) && lastKeyState.IsKeyUp(Keys.Space))
                    screenState = ScreenState.PLAY;
                break;
            case ScreenState.PLAY:
                break;
            case ScreenState.EXIT:
                break;
        }

        lastKeyState = keyState;
    }