Aaah, it's one of those games.
It wasn't mindblowingly great, but sertainly wasn't booring either :3
Ways to improve :
Add a menu ( yea i know it's a boring process, but it actually makes the game feel more complete )
Might even make the character slightly bigger so you better see what you are controlling.
Background graphics, i noticed you're a programmer, well same here, but there are loads of people to ask for simple graphics. But who knows, maybe you are as stubborn as me and need to make everything but the music by yourself :p
Make the game screen more horizontinal, it would give the player a heads up for what's coming. But it ofcourse comes at a price, the price of not paying as much attention to where you are.
Anyways, i hope some of the tips were of use, have a good one :)