Hey, so, first of all: Excellent game. This held my attention for quite awhile, I really only stopped after my arm started to hurt too much (tendon problems, cant use mouse for long, gonna have to rig up a controller scheme, will try that later).
The different "biomes" are really well done, and the exploration never stopped being tense and exciting, even though I tended not to move very fast.
Seriously I think you're onto a real winning formula here. This is a game I'll probably be coming back to a lot... exactly my sort of thing. I'm a huge fan of the Backrooms concept (particularly after Kane's excellent new series) and this captures it well. I'm really hoping that you'll keep expanding it, there's so many cool concepts that could appear here.
There are a couple of frustrations that I ran into though:
The biggest one is the flashlight... I quickly developed a loathing for that thing. I also learned to never touch the A or D keys, because that made the wobbly thing go all over the place.
But also, the dark areas: There's just too much of that. I dont know how many would agree with me, but I find that the freaky/uncanny factor drops quite a bit when in dark areas, because I cant see the stuff that normally would be generating that atmosphere. When in that type of area, it often just felt like exploring a mundane hallway... definitely something lost there.
That, I guess, would be my biggest suggestion: Way more lit up areas, way less dark areas. The dark zones would probably be that much more freaky if they were only encountered every now and then. Particularly if the player had been in a lit up area for a good while, and then POP, the lights flicker and go out.
Also the glass walls: I got stuck on those OFTEN. Dont get me wrong, they absolutely work in terms of atmosphere and such, but combined with too many dark areas and... yeah, I spent A LOT of time smacking into things on floor 3.
There seemed to be a couple of bugs, typically textures acting odd or doors that seemed to get eaten by the walls after a moment, but nothing that actually interfered with the gameplay or experience.
Oh, and the fuzzy video effect is really well done. Seriously, that's impressive. Excellent job on that. The sound design is also excellent.
The one thing I couldnt quite grasp though was the rising water event that would happen every now and then... did I do something to trigger that? Is there a way to stop it?
As it is, I got to about floor 9 before I had to stop for the day. It was great the whole way through. Oh, and is there a proper way to exit the game? I couldnt find one, had to alt-tab and close it that way.
One last thing, I know the idea of having some hostile things in the game has probably been brought up, and I do think it could certainly be done well, though if it were up to me, the player would only encounter said creatures every now and then... too many encounters and the game loses that empty aspect. Besides, monsters are going to be so much more effective when you just arent expecting them at all because you havent been seeing any for awhile. Not that the game NEEDS monsters, of course. But I bet you could do it quite well if you should decide to.
Anyway, so that's everything I wanted to say! Very much enjoying it so far! Cant wait to see what else you might do with it.