It's a well-made boss battle scene. It's not just about the boss - you get many different kinds of enemies in waves. You also get different, nicely themed power-ups with your appearance changing accordingly, so it remains interesting even though it's a long battle and you may need to retry. Overall, the character designs look nice and the music is good too.
I'd like to invite your game to our Game Development World Championship! I think it could have a good chance, especially in the jam entries category.