if(SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"6.0"))
{
    GKLocalPlayer *localPlayer = [GKLocalPlayer localPlayer];
    localPlayer.authenticateHandler = ^(UIViewController *viewController, NSError *error)
    {
        if (viewController != nil)
        {
            AppController *appDelegate = (AppController*)[UIApplication sharedApplication].delegate;

            [delegate.viewController presentViewController:viewController animated:YES completion:nil];
        }
        else if (localPlayer.isAuthenticated)
        {
            NSLog(@"Player authenticated");
        }
        else
        {
            NSLog(@"Player authentication failed");
        }
    };
}

- (NSUInteger)application:(UIApplication*)application supportedInterfaceOrientationsForWindow:(UIWindow*)window
{
    return UIInterfaceOrientationMaskAllButUpsideDown;
}