Fortunately I had another idea that is something much more up my alley. A puzzle platformer that uses the corpses (bone piles really, let's not get visceral) of the player character in order to solve puzzles. While it's not as original as my first idea I'll be able to quickly get the game into a playable state. That, and I also just like puzzle games and platformers, so it'll also be more fun for me to test the game. One thing I'm slightly worried about though, is that other participants will have had an idea very close to mine. I wouldn't effect the objective quality of my game, but the effect of scarcity and uniqueness is a real thing, so we'll see.
Look like I am going to have to use Box2D though. I want the player to be able to throw the bone piles they left behind in order to solve puzzles and defeat monsters.