It played fine on SteamDeck after I searched up which version of Proton to force it to run under, and did some controls mapping.
That said...It's... Just the demo.
Unintuitive boss fight mechanics, a one hit kill and a three life maximum (before the game resets itself!) means: I just kept repeating the demo for the vast majority of my play time.
I could watch a tutorial on the rest of the bosses, but honestly the later levels (that I have reached) are just different paint added to first level.
6/10 - It's surprisingly good for being one of the earliest attempts at a making a 3d game.
If I was going to replay it, I would seach up a boss fight tutorial first, to save myself time. It's just not worth playing through the whole game each time I want 3 more chances to guess each under-communicated boss mechanic.