This was fantastic! The atmosphere throughout is perfect, absolutely filled with tension. The audio design is superb too, and really adds a lot to the experience.
I really enjoyed the way you developed the narrative through the memos and emails etc., you struck a good balance between explaining enough to make sense whilst retaining some mystery.
The phone is great - it's a nice way of including objectives and notes diagetically, and is really straightforward to use. I'd love to see more bits like the QR code scanning at the start! I also thought that the audio meter was a great concept. My only complaint was that it'd be nice to have a way to reduce the amount of screen space it takes up when not in use.
I'd love some kind of checkpoint system as I found it very easy to die once the monster appears, but understand why it's not in place from the comments in your devlog. This is also probably my own fault for panicking and running away instead of sneaking!
Regarding physics, I found that the Amnesia style physics interactions really didn't play well with my mouse, opening doors and turning that valve took a long time. My mouse is absolute shite though, so that could easily be on me. Is there a way to add a sensitivity slider to the options menu at all?
Apologies for the essay - I really thoroughly enjoyed this one and wanted to give detailed feedback, hope that's ok! Good luck with the jam :)