There are a lot of ways this game could be enhanced. Why don't you try a few?
The game currently lacks a pause option; why don't you add one?
Our game is naïve with regards to multitasking. Upon resumption, it will happily extrapolate where we should be in the cave after what might be a very long time. A better method would be to pause the game when it is in the background.
We're using pixel-based collision detection. Why don't you try to use math-based detection instead?
Try various control schemes until you find some you like.
Use gyroscope values if available.
Add powerups or other objects in the map that could affect the player for good or bad.
Make static levels for the game that could be loaded on demand.
Add logic to make sure any level is winnable.