This was a really atmospheric one - the lighting and setup was this oppressive atmosphere that felt like it would creep in on all sides. Every time I saw a closed door, I was checking it on my next pass to make sure it hadn't opened, constantly watching corners expecting something to jump out.
The lack of any jumpscares in my runthrough was promising - because it let that tension ride, and rise, and I could never tell if there even WAS a monster lurking down there in the dark with me.
I made it to the end without ever encountering anything - which until I read through here, left me wondering if it was genuinely something even in the game, or if I'd simply gotten lucky. It gave me the same feeling of a horror movie, where you can see the danger is just right behind the protagonist, but they never realize just how close to the edge they were.
With a proper ending scene added this would have truly slapped - because for playthroughs like mine, it would've made it abundantly clear that I was in fact not safe.
The sound design was awesome - everything feeling old and graty and clunky really made the entire place feel ancient. The visual aesthetics and that crunchy pixel look also added to that horror feel, like I was watching this all through a found recording. A solid use of lighting really sold the atmosphere - with my only critique, like others have said, maybe being to use that light to indicate visually where you need to go.
The opening space and finding the actual entrance to the side rooms took me a good minute - but I felt like scouting out the unknown doing so, and once I realized what I was hunting for, the puzzles all started to click into place.
A really fun puzzle horror game. The tension building was great here.