×Certain shuffle-a-bunch-of-monsters-in-a-box rooms (lvl 15 1W, lvl 9 2S 1E) are breakable, because movement order. You can get away with luring less monsters in the "box" than it is intended. Ends up being more efficient so this is go-to solution if it is possible. Probably fixable by forcing player to move back-and-forth above/below box to "shuffle" monsters (or at least it makes breaking things *way* harder). Might be worth considering it when designing puzzles of similar type in the future.

I'm still not sure what's the difference between level 7 1N and "secret" variation because I used literally the same approach for both.

There probably were a few more maybe-unintended solutions but can't really remember right now. Probably nothing notable.

I felt like 11th level went overboard with path-planning rooms (1S 3W, 2S 3W, 1S 2W is pretty similar, 1S 1W also has similar idea though much easier). I feel like just 1S 3W and a secret variation would be enough. Then again, maybe I'm biased, not biggest fan of puzzles like this in general. But IMO there are more different things that could've been done with invis potions than what was shown in the level.

I'm really not sure why there're two serpent-introducing levels (and why there're semi-tutorial scrolls about serpent movement in 10th level entrance). Aside from a couple of rooms 5th level ended up being a bit weak. 10th I liked. Maybe it was worth merging them in one level.

On the plus side: Some of the puzzles in the first few pure-roach levels, are pretty impressive, especially considering element constraints. Brain, mimic, tar, tar mother levels were loads of fun. Last levels (17th and beyond) are high quality and quite tricky, too.