private static extern void _LoadAchievements(LoadAchievementsDelegate callback);
 /// <summary>
 /// Loads the local player’s current progress information from Game Center.
 /// Should be called immediately after the player is authenticated.
 /// </summary>
 /// <param name="callback">Callback will be <c>true</c> if the achievements are successfully loaded,
 /// <c>false</c> if there was a problem.</param>
 public static void LoadAchievements(LoadAchievementsDelegate callback)
 {
     _LoadAchievements(callback);
 }