Cute concept! I like the sprites.
I've done 3 runs, and haven't found any of the alternate weapons, but the powerups feel powerful and unique on their own.
A little more enemy variety would be nice, but the search for the boss, and then his fight make the loop interesting enough.
The lighting is very nice in the second level.
I think the bosses placement is fixed? If so, that would be a spot to improve for replayability.
An little more of an ending screen would have been nice, some kind of narrative or something.
Edit: I just went back, determined to find the alternate weapons. I found the staff in all 3 stages, and it is incredibly op, especially in the third stage where you can hit the boss from a spot it can't hit you. I don't think the staff being op is bad, just wanted to comment on it. Maybe the bosses attack should be able to go through walls and not collide with itself though.