So I'm making a game engine, a "general purpose" (I guess) game engine for 2D platformers and RPGs and basically anything that can be represented as stuff on a 2D plane.

I'm just wondering if anyone has any suggestions for things I can add to the engine, like features and whatnot. Or if you want you can give a general overview of a game and I can see if it can/will work in my engine.

This isn't actually a promise to make any games, mind. So... Uh, no free labour for you. I'm just looking for things I've overlooked.