It should've been common sense for you, the developer. Mac OS X has always been 64bit since apple moved to intel architecture.
Huh. If you're learning and this is your first game, it SHOULD be common sense to not release it. Nobody comes to these sites to check out an experiment from some person who made it as a learning exercise. You should not be releasing games unless you intend to actually release them, not to put them online as your 'first game'.