I really dig the graphics and sound (except the white-on-blue text, it’s a challenge to read).
This could be improved by making jumps terminate when you release the key, and by allowing horizontal motion mid-jump. As is, everything depends on starting each jump at just the right place. It’s hard to judge, and that makes it maddeningly difficult.
Also gamepad support would be a big help.
Overall, it’s a solid little game. Gives 8-bit console vibes, in the best way :)