What a great concept and execution. Not to mention an impeccable GDD :)
I don't know if it was Proton-related (ran it under Linux Steam), some instability in my system or something else entirely (maybe how many times I died to the spikes!) but I was able to reproduce several game crashes on the... maybe third or fourth level, with the spike pit at the bottom? Seemed to occur after about three or four deaths. Other jam games including some quite demanding 3D ones (and other Unity games) have been performing well, so just thought I'd mention it in case there was an issue with resetting the player after a death or some such.
It's the kind of thing you only find out with people like me who suck at platformers!