It's fun, but three things stood out to me that made it less fun or at least feel like it was missing something.
1. Since you might die often, it was a bit inconvenient not having a "Play Again" button or something
2. No visual feedback for hitting an enemy. I think a flash red or something like that could go a long way
2. Upward thrust feels great, but the linear velocity of falling down seemed kind of off for me. I think I just expected at least a little bit of downward acceleration when not going up.
I actually like the art by the way. Maybe some details in the walls and stuff would help, but the enemies and character seemed good to me.