Overall I quite liked it, it felt really charming. There were a number of smaller things, most of which others have already pointed out, but there was one issue in particular that I do feel the need to mention: I really didn’t like how the camera worked. It was rather slow to catch up to the player, and it went in the exact opposite direction than I thought it should. By which I mean: if the player is going right, it should be even further right, putting the player at the left of the screen. If the player is falling, it should be below it, putting the player at the top of the screen. This way you’d have less blind jumps and enemies surprising you from off-screen, which feels unfair rather than simply difficult.
I think changing this wouldn’t be all that difficult, but would significantly increase enjoyment (for me at least).