Predictably and completely brilliant considering the people involved. I thought the difficulty curve was spot on — not the sort of puzzling death march that requires you to bash your head on a level for days, but stuffed to the rafters with deeply satisfying and hard-won a-ha moments.
I felt C4 had a very Le Slo sorta vibe, so was pleased to see that was indeed a Le Slo level. And I was delighted to see the D7 mechanic finally surface after what-iffing on so many levels that by the time I reached D7 initially I didn't even consider it.
10/10 would slime again.