In my opinion, the only real drawback of the game is the lack of a Web version. The game itself is very good, with different themes, various enemy types, and multiple platformer mechanics. It took me about 5–6 minutes to start and finish the game, and it was very comfortable and easy to play.
As for shortcomings, the only other point — also mentioned in other comments — is that the boss hit feedback felt a bit weak. Adding a slight knockback or a small hit effect could improve the impact.
Overall, this was the best game I played in the jam. Congratulations!