I mean, the entire game is a masterpiece. The graphics, the soundtrack, the animations, the story and the way it is told, the characters...
It's one of those survival horror games that will really put you on the edge, almost always putting something life threatening in your way
The puzzles are pretty smart too. Sometimes the way you move can be troublesome and trigger some trap or something, but aside from that, thinking the puzzles and solving them is a pretty solid experience. The password system is also great, since it gives you every item you need to have in any given room you put the code for. Every password game should be like that, because that's the point of having passwords I think. No reason to "skip ahead" with zero items.

The only really bad part is that worm detector part. Fuck that part.