I really liked the environment, it had a great color scheme and felt very inviting at the start, but the change in lighting helped bring out the isolated vibes. The visuals (especially outside) are the strongest area this game has going for it in it's current state.
I think the game is mostly lacking in clarity. I feel like the setting and characters were underdeveloped and the pipe scanning mechanic could be explained better to avoid confusion. The subtitles often disappeared quickly and there wasn't really a way to check your objective as far as I could tell, so I had to restart right at the beginning because I didn't read or hear in time what to do after picking up the scanner. I think an interact prompt on the pipes would be great to add.
The corrosion scanning mechanic is a pretty cool idea. I think it needs to provide more feedback for the player though. It mentioned a score of 1 being perfect and whatnot, but I didn't notice where a score was being displayed? It was maybe a little unclear if my scan was acceptable or wasting too much material. It would be cool to see how it would get developed further if this game gets future updates.
Like others have mentioned, the table and shelves do not have collision. I'll also point out that the scale on certain things seems pretty off. The lockers seem tiny and Mark seems giant, towering over the player like we're a child. Oh also I noticed some sideways grass on the walls of building D haha.
Some of the jump scares sound like an electric guitar which I found a little funny. The jump scare in building D where I think boxes get knocked over or something got me though, that one was pretty good! I also found it pretty eerie seeing the monster looking at you from the windows in building D, I liked that. It would be really cool if the head slightly turned to look at you as you walk below it.
I think you did a good job at raising the tension between each task. The interiors felt uncomfortable and outside felt less and less inviting. I liked the plot twist, though I found Mark's death a bit comical. Having to run from the monster was pretty fun. Not sure if you're doomed or can actually escape, but I died and I really liked the ending.
Overall, it was pretty enjoyable :) good job!