Hey man, pretty neat little game here.
I'd love it if you could add in a crosshair, just to help a little with the aiming accuracy. Also one or 2 more maps, with some slightly different design and themes might help sell the idea better. Perhaps even some objectives, or collectables, different enemies, projectiles etc... I think it's a neat idea, although I'm not sure how much legs it has in terms of a 'full game'. Would definitely be cool to incorporate this as a 'challenge mode' or something for a full campaign type fps, although I think you'd have to try and gauge that better once you have some more feedback. I do like it though. Kinda reminds me of some old school 90's/early 00's games.
I'd definitely play more!