thanks for playing! you're absolutely right, the undo system is not communicated at all in game and is quite lacking. i really wish i had figured out a good way to implement a complete puzzle reset system, to save long undo sequences, but i just couldn't figure out a nice way in any reasonable amount of time.
i did fix a couple of puzzle designs that i was sure would practically guarantee long boring backtracking sequences, but of course, that's not quite enough to save the game from all the boring backtracking.
i'm honestly super touched to hear that you thought the music and sounds were good! those are areas i'm not as sure of myself in, but knowing that at least one person thinks they're better than my art is, weirdly enough, actually extremely reassuring lol.