In my code (based on the ShootEmUp example in this book, which I highly reccomend, source code in chapter 8 available here) I often use the trick of accessing the GameScene via:

+(GameScene*) sharedGameScene;

which returns a reference to the static instance of GameScene. Is a static instance of GameScene as in the book still a valid pattern in case I want a MainMenu calling GameScene initialized with different level data each time (e.g. different enemies)? (I have created a sceneWithId:(int) method where I load different level data each time.

Or should I pheraps create a GameScene class and then sublcass it?

E.g. FirstGameScene : GameScene