This was a fun one, great challenge and the boss fight was really well designed. I thought I had figured out a way to cheese it by coming in close and spamming boomerang, so that it bounced off the wall faster, and then the boss did that big blue circle push-back attack and it was like "ok, game on." Really cool moment, and the boss has a nice amount of variety in their attacks too, that's impressive.
It looks like the character art was made by rendering 3d models as pixel art, which is really cool, I like the art style a lot. The music fits perfectly too, it matched the frenetic action of the gameplay.
This could definitely be further developed into a full commercial game with some more rooms and bosses added, the mechanics are solid. It would make for a great family-friendly version of a Hotline Miami style game.