/// <summary>
        /// Adds a new screen to the screen manager.
        /// </summary>
        public void AddScreen(GameScreen screen, PlayerIndex? controllingPlayer)
        {
            screen.ControllingPlayer = controllingPlayer;
            screen.ScreenManager = this;
            screen.IsExiting = false;

            // If we have a graphics device, tell the screen to load content.
            if (isInitialized)
            {
                screen.LoadContent(content);
            }

            screens.Add(screen);

            // update the TouchPanel to respond to gestures this screen is interested in
            //TouchPanel.EnabledGestures = screen.EnabledGestures;
        }