Jumping mechanics are actually quite fun. I think you should totally expand on this, maybe clean up the graphics a bit (keep with the flat colored MS Paint style though, it's quite charming), add some new mechanics and/or obstacles. Maybe speed up the gravity a bit? It would be harder, but the speed would make it more fun, I think.
Of course, that's all if you want to, I'm not gonna tell you how to spend your time.

quite fun