The game succeeded in teaching me a whole load of mathematical concepts that I either didn't know or had long forgotten, and did so in a way that made me feel pretty smart for figuring stuff out. The gradually unveiling structure was good for keeping the challenge space manageable. The puzzles were on the whole challenging without being too obtuse-- I only resorted to hints a few times and mostly discovered I'd forgotten to look at something properly.
I'd give it 8.5/10: very good execution of the concept with few missteps. Relatively sparse environs and characterisation, but this is fine for the kind of effect it was going for.
84 rooms, each written by a different author, but co-ordinated into a structure and based around a tight enough theme that it all hangs together though often with intriguing incongruities.
Roughly, you can split the rooms into two different sorts: rooms which function as typical text-adventure rooms (a key might be hidden somewhere, there might be a short puzzle to get it); and rooms which are short games in themselves, which immerse you in their own unique stories, force you to learn a new set of interacting systems and so forth. As such, the game is constantly confounding your expectations.
Some of the rooms are genuinely horrifying, others are laugh-out-loud funny, more still are challenging and satisfying to work through. I recommend to anyone who likes text adventures especially its inspiration, Anchorhead. Expect to need hints!
(I contributed to this game, so per my own policy I've omitted my rating from the average.)