As someone who put tons hours into Vampire Survivors, I dig that you made a bite-sized version that would meet with a Game Boy requirements in terms of gameplay and visuals. The game's length already has replay potential for different power-ups and that "one more try" feeling when you lose (which is easy to do if you're reckless), and the enemies are unique with their own special traits. Almost made it to the end and beat the final boss but this was still cute.
Great job making this. The only thing I would add is if there were more weapons and you could only hold three at a time. This would add a bit more attack variety, but as is, the game is fine and challenging enough with more fish. Would've been 11/10 if I pet Churro, though.
If you like, you could try out my game about a forgetful goldfish.