I really liked the take on the limitation! Becoming the boss creates this interesting dual gameplay, where you try to survive and then try to die. (I would have liked your HP to carry over though!)
I got stuck at the end of the second level when I accidentally killed both the zombie enemies by the time they did only half my HP of damage. Not sure how I was supposed to do that, since I seem to damage them on contact too. And then there's no game over and no way to get out of the room.
Some things I would have liked to have seen:
The jump is a bit floaty, and the platforms seem a bit too close together, making me consistently bump my head against them. Some tweaking of the jump might be helpful. I imagine the later levels include this to some degree, but more and more difficult solutions for killing yourself at the end (almost like a puzzle game at the end of the platformer/sidescrolling shooter game) would be interesting to see. Also, music.
Anyway, a pretty clever take and a nice game overall. Well done!