Really nice job! It's short, but there's not much you can do about that in a game jam. I saw that you put a lot of your time & effort into the art, which payed off - because it looks great! And even though you put a good amount of time into art, you still were able to create good gameplay that does not feel like there's anything wrong with it. Good job, make more games.
All that I can think to add later on is more areas to explore, probably more going on with the boss, perhaps things that change up the gameplay - but overall it was a really good job with your usage of time.
I would also appreciate if you rated my submission, I'm trying to rate a lot of games - so if you do too that would be greatly appreciated.