Have you noticed anything odd about this Home screenshot? That's right! The next release of Home should be o3DS compatible! Only drawback is no world shadows, but it's fine. I won't release it this week though because I've been spending time with family for the holidays, though now I can start work again.
Callbacks? In my BASIC?! I manage all sprite collision through a single object operating on plain arrays. When two things touch, their "onHit" method is called. Anything not actively being controlled by a player or AI doesn't require an update! THE SAVINGS!!!