Hi, the game could have a lot of potential. I ran into the following problems:

-Really Really hard to sneak past first 2 zombies without attracting them
-The dialogue box should write out the full controls (in case people get confused with the acronym LMB or Lewy CTRL)
-I got stuck after getting the ammo pack, it seems like the ammo pack adds 30 bullets to the ammo maximum and not to the gun's current ammo (I'd go from 0/90 bullets to 0/120)
-I could open the developer's console (don't know if this was intended)

I really loved the UI and Art style and as a prototype I could see where you're heading. I'd say if you polish gameplay and the tutorial and add some animations this could be a lot of fun.