The atmosphere is really great. Love the shader you used, it gave an awesome retro vibe. The stealth vibe and setting were an excellent choice.
The enemies seemed able to see me even when crouching and hiding behind stuff. I also tried the flashlight on them but I didn't notice much difference. I also agree the map was a little too empty, but at the same time that gave it some sense of realism and scope.
Overall this game just needs a few small tweaks,. It's really good!