public SceneManager(ContentManager contents)
 {
     _allScenes   = new List <Scene>();
     _contents    = contents;
     _activeScene = null;
     _preScene    = null;
     _isStarted   = false;
     _gameState   = Managers.GameManager.GameState.None;
 }
 public void Update(float deltaTime)
 {
     if (_isStarted)
     {
         if (_activeScene != null)
         {
             GameManager.GameState state = _activeScene.Update(deltaTime);
             _gameState = state;
         }
     }
 }