Instance C - MainGame

if ([node.name isEqualToString:@"backButton"]){

        SKScene *mainMenu;

        if (!mainMenu){
            mainMenu = [MainMenu sceneWithSize:self.size];
            mainMenu.scaleMode = SKSceneScaleModeAspectFill;
        }

        if (mainMenu){
            SKTransition *transition = [SKTransition fadeWithColor:[UIColor blackColor] duration:1.0];
            [self.view presentScene:mainMenu transition:transition];
        }

    }