Here's what's next:
1. Gravity - Should be trivial, but at the moment the player moves in a straight line.
2. Jumping - A little trickier than basic movement along a straight line, but shouldn't take too much time.
3. Refined Collision Detection - The collision detection mechanism I have now is a little hacky.
4. Enemies - The game is no fun without bad guys!
Alright, this should keep me busy for a while. I'll see if I can get a video of the current state of the game up sometime later this week.