Really good game and I had fun while playing this! For improvements, I would definitely love if there's more feedback (i.e. flashing the sprite white or red when hit, adding a health bar to the enemies, adding knockback, adding damage numbers) when shooting enemies as it's quite hard to tell if I hit them or not especially for the boss fight. I've also noticed that the footsteps sfx is much louder than the background music so I would tone it down.
Other than that really good game with a very cute artstyle, good job and keep it going!