Gameplay highlights for me include how the triangle in particular uses its shape to kind of "grab" onto platforms to get a bit of an edge, it just feels right. I'm not sure if it was intended after getting the pentagon, but jumping over the tiny, cramped spike pit above it with triangle's grabby double jump was a nifty little moment after getting denied by going through that as a square and lacking the jump height to proceed. The way you can only swap shapes at these shape swap spots made it quite fun to figure out what shape I was going to need to get past the next obstacle and actually to the next gate. This process could expand out to quite some intricate puzzle platforming when explored further with all the shapes in your tool belt.
I appreciate the visual aesthetic you squeezed out of these basic shapes, by giving them these nice gradients, presenting the shape swaps like a little confetti pop of sorts, and how they have a nice spin when jumping. The darkness in one of the area adds a pretty strong sense of being in the endgame, and the music is a bop all over. The fact that the music itself is also basic shapes is very clever!
Regarding technical hiccups, I'm not sure if I'm missing something, but it seems that dying as a square in the triangle area gets me stuck. I couldn't you can't reach any of the shape change gates as a square from the starting spawn point, it just doesn't jump high enough to get to the first shape swap spot. Might just be how the patched version handles the respawns though. Treating the shape swappers as checkpoints would probably be helpful here, given that there's more traversal and problem solving than there is combat anyway?