It's alright. A good platformer. It's fun, has nice hidden collectables.
I did have a few issues: Offscreen blocks stopping me from moving, being unable to move down whilst on a wall, and the up button being mapped to jump but not swim, kinda messed with me.
It took a while to get used to the engine. I like that it's quite unconventional, but without proper places to get used to the mechanics it came off as frustrating to start with.
The head banging felt too sensitive, maybe instead of fully removing momentum let the player continue moving horizontally slightly?
Saving would be a nice mechanic, (PICO-8 does support that!) I unfortunately didn't get to the end because I tabbed out and didn't want to restart...
I like the little quips the character gives when running around, that gives the game a lot of charm.
The game kept my attention for a just a bit under an hour. It felt frustrating to control at times and I didn't finish it, but it has a nice unique engine and artwork. I would suggest playing this if it was brought up. (: