Very interesting concept, the lighting and all the post processing was very nice, and created a nice looking atmosphere.
I hate to just repeat what others have said but UI showing the possible controls, whilst playing the game is definitely needed.
The lack of SFX for this game doesn't cause too much of an issue in my eyes but it would have created a much better atmosphere if they were present.
Overall the concept is very good, and the atmosphere and controls are nice. Just them two things that are holding this game back from being really great. Well done :)