I know this has been out for quite some time but i've just seen the youtube video and figured I'd give it a try!
Love the simplicity of it, and the fact that it was made in such a short time! Would definitely benefit from Forgiveness Mechanics like Coyote Jump, Jump Buffer/Input Buffer and reducing the collision hitbox for the boss as well as adding some sort of telegraphing animation that he's about to hit (his attacks are pretty sudden and I believe you can get hit by the arm as well, not just the claw?) Lastly, would very much help if there were some invincibility frames so the player doesn't lose 2 of their lives every time they mess up. I understand most of that needs time though, so for the time frame, this is definitely well done!