I like the art style and music, I think if you had a more recognizable character design it would launch the art direction to Double-A.  A tutorial would be nice, as I also didn't know there was a double jump and got stuck at the beginning.  some of the enemies are very small and not hard to see, I died many times to things I didn't see in the moment, perhaps if something can hurt you it glows white instead of just being its base color?  the sizing issue I mentioned before, however, it makes it hard for me to see the end-game menu, and I'm not sure what most of the buttons on it do. (this critique boils down to making the death screen more intuitive) I don't know how you generate levels whether it's procedural or hand placed but they are really nice.