I'd like to include Game Center support for devices with iOS 4.1 or higher. As far as I can tell, the only way I can compile using the GameKit classes is with Base SDK 4.1. When I select Base SDK 3.X, even with the GameKit framework included, my app will no longer compile because the GK classes are missing. My question is: if I compile with the 4.1 SDK, will 3.X devices be able to run the application (minus the Game Center support, of course)? Since I don't have a 3.X device, I have no way to really test if it works or not. I'd like to make sure 3.X is supported since a lot of people haven't upgraded, but I also want to include Game Center support for devices that have it.