internal static void AddScreen(Screen screen)
        {
            foreach (Screen scr in screens)
                if (scr.Name == screen.Name)
                    return;

            screens.Add(screen);
        }
        internal static void ActivateScreenByName(string name)
        {
            prevScreen = ActiveScreen;

            ActiveScreen = GetScreenByName(name);

            if (isStarted)
                ActiveScreen.Initialize();
        }
        internal static void ActivateScreenByIndex(int index)
        {
            prevScreen = ActiveScreen;

            if (ActiveScreen != null)
                ActiveScreen.Remove();

            ActiveScreen = GetScreenByIndex(index);

            if (isStarted)
                ActiveScreen.Initialize();
        }
        internal static void ActivateScreen(Screen screen)
        {
            prevScreen = ActiveScreen;

            if (ActiveScreen != null)
                ActiveScreen.Remove();

            ActiveScreen = screen;

            if (isStarted)
                ActiveScreen.Initialize();
        }