It almost looks like a mission pulled from the base game, but I find it annoying and tedious. I'm surprised by its high reviews, really. The tiles add challenge, sure, but not in a satisfying way - more just an irritation. I had a couple moments where the sound propagation was clearly bugged and people were hearing me from many walls away when they certainly shouldn't have. Level design is otherwise annoying as well, with specific paths to take to backtrack and too many doors requiring keys. I'm not sure I'd call it outright badly designed, but it wasn't for me and I couldn't bring myself to finish it. I do admire the effort, though. The author is clearly experienced and skilled.

Maybe I'm just not used to this kind of level design yet, having played very few FMs.