Good idea, solid implementation. Style, art and sound are consistent and create an atmosphere, which is more important than heavy detailed assets. You did a great job of keeping the scope small, but polishing it and making a finished game! I'd like start/restart button to be pressed with space as well, it would be easier than switching to mouse every time between stages. Also it'd be cool if enemy slowly pulled a gun and died mid-animation, so I can see how much time I really had and how difficult the level was. Overall great job!