I played your game and i surprised myself trying to find some cool strats to overcome the main issue with your game : it is too difficult. I managed to score 168 which is not bad (i think) but I reached a point where there are more enemies to kill than my weapons can (I every shot was done correctly).
An other point : I am not a fan of the atmosphere and the game lacks of depth : only one enemy and one way to shoot.
It was nonetheless interesting so well done :D