Interesting world you've created! Slug guns to battle zombie clones of yourself. I have to admit, I haven't seen that one before. I dig the art style and music, it is bleak and dystopic.
Two game mechanic suggestions. One, I'd allow the player to jump again as soon as they hit the ground, like most video games. Second, I'd give more ammo of each slug, maybe 4 for a heavy hitter, 12 for a pistol. These two changes would prevent the player from losing key "Verbs" while they play. You could up the enemy count to compensate the difficulty balance.
All in all, a memorable and novel experience. Best of luck in your game dev journey!