Origonal gameplay! I love how you can shoot out windows to quickly clear a room. I feel the difficulty is a little too much, it took me many tries just to clear the first room. Also I would change either the fog of war or the field of view of the camera, because most of the deaths happen from enemie that you cannot see. I noticed that the most efficient strategy is to shoot far outside your field of view, be it windows or enemies.
That said, I would really be interested in what direction you're gonna take this game. It's a very solid system and It could work both as an action and a more tactical shooting experience. Great job!