This is quite cool! I can see the bones of a stealth game here; it's quite cool to be able to sneak around corners and take out enemies without them seeing you. How quickly enemies can kill you definitely encourages a more cautious approach, in the same manner as a game like Hitman. The level layout is quite nice, and the fog combined with the textures gives it a good atmosphere. Sound effects are satisfying. In terms of what to add, I'd like to see a clearer "endgame", and goal for the player.