Nice Work! Really nice game. Definitely works with the theme and I like the different attacks and the sprinting mechanic.
I think adding some sound effects would really benefit this game as a way to give the player's attacks some more weight and also as a way to tell the player that they have been hit by a bullet.
Try giving your player character a white outline (when yo have a dark background like this) to make him stand out more from the background. Its a nice way to draw the player's eye to your player character.
Keep up the good work!