This had a lot of issues, but I gotta say if you added some features and fixed the bugs, this could be a really really fun game!
Problems:
I had a bug where I could move after I died so I had to restart the game completely.
Picking up the limited ammo was annoying as I had to wait a while for it to respawn.
The aiming was off for me. I would have the crosshairs right on the bad guy and would miss so I would have to adjust it and "miss" intentionally to hit them.
Suggestions:
I think a rolling mechanic for the player would be perfect and so fun for this type of game.
Picking up ammo is good, but I would add a reload mechanic as well, where if you run out of bullets you have to reload each bullet one by one, which takes time and puts pressure on you while you're reloading. I'd have more ammo present and make sure enemies drop loot.
Adding upgrades like ammo capacity, damage, accuracy, fire speed would be great.
Adding more types of enemies
Awesome work! I see a future for this game if you keep at it!