Creepy vibe always gets points for me, very neat aura. Just the positioning and layout of certain spots just reminded me of Half Life and the facility level in Goldeneye. Also love the surreal "sort of" real look to everything, really messes with your head in a good way.
One thing I'm not sure was intentional, there was a green cube early on in a corner and I meant to size down but sized up instead, and it seemed to disappear. I think the space it was in would not have allowed a larger cube so maybe that had something to do with it.
I agree with Lanyard about nudging the player, at least until you get into the game a little bit and they're familiar with the basics. Overall, really enjoyed this one.