The art is great, especially the backgrounds and the animated enemes. Could have taken it to the next level with parallax, it looks like it was already drawn in layers anyway. One minor nitpick is that there were one or two areas where there were seams in your tilemap. Really appreciate the checkpoints, I was very worried on my first death I was going to have to start all over. Music is great, always nice to see multiple tracks, and they fit their areas well. Sounds are solid, not annoying which a lot of repetitive sounds like jumping can sometimes be.