public static void RemoveLoadGameSceneListener(OnLoadGameScene callback)
{
if (_instance == null) return; // could be called during game exit
_instance.sceneLoadListeners -= callback;
}
/// <summary>
/// register a listener to notify when LoadGameScene() is called (true is passed to callback)
/// and also when the scene is done loading (false is passed to callback/listener)
/// </summary>
public static void RegisterLoadGameSceneListener(OnLoadGameScene callback)
{
_instance.sceneLoadListeners += callback;
}