Man, this game's a tough one. But you did a fantastic job with it. The controls are tight, the movement feels fluid without getting too floaty and the art & concept are great.
As others have mentioned, the jump does feel like it could go just a little higher, as it was a struggle to get through the opening levels because I kept hitting the edge of platforms rather than getting on top of them.
Overall, a great project. Honestly with some good music & sound effects, I think you could turn this into something marketable.