The tilesets are great, there's no mismatch here and there and capture the feeling of post apocalyptical zombie thingy. I love how you make sure the player get enough ammo to plow through the final zombie.
Also I didn't see the function of health when you just die when Zombie touches you. Yes steams kinda reduce your health but I think there's no penalty of going through without full health. Maybe if the development took time to refine the mechanics and submit it later, those other feature can give some point/ meaning.