It's pretty good, a few things that I think would make it better is:
- Add a way for the player to score or add a stopwatch timer and record how long the player can go.
- Add obstacles the player should avoid.
- Add some SFX to make it less quiet. Bfxr is good for simple sounds.
- Add some music maybe, Bosca Ceoil is good for this.
- Make the level randomized if possible unless it already is if so, good.
- Make the ball/circle roll rather than just slide. (Basically rotation).
You have a good basis to work off of, and you can make something interesting with this.