I am watching Apple's overall intro to Game Center. It says that to be a game center game you have to:
1) Register your bundle ID through the developer portal.
2) When your game is launched, you have to authenticate a game center player.
Is it OK if I make the authentication part optional, and if it happens later than launch?
So my users can play the game without GC if they want to, and then add it in the middle of a session if they decide they want to do that.