I only got a maximum of 2 enemies. Then nothing happened (just jumped around a little until I killed myself^^). Same for the next 2 tries. On the last try I even only got one enemy. I guess it's a bug? A highscore system would be cool for the game if it worked for me ;)
Kudos for making your first game! The idea is solid, but I'd like to see more enemies and more of an environment. I think the large boxes should be static, as having them move when you run into them doesn't feel right. I like the visual for the enemy - kinda spooky. Keep at it!
More UI (Ammo, Kills)
Reload animation
Music