What a cool game. Everything really comes together here but I especially love the first enemies you encounter. The way they act like they're watching you and stalking you is so awesome. Atmosphere is great, the movement feels really good. One thing I'd say is maybe I'd like a little more feedback from the player's weapon, it could be more satisfying to shoot. That could be some punchier sounds, a slight camera shake, etc. Also with how precise the weapon is and how precise you have to be to hit the red spot on those enemies, a bullet trail would be really nice visual feedback. Think like Halo's sniper rifle bullet trail.
But overall, I absolutely love this and want more of it. Great job!