Hello,
this is pretty much like the begginer tutorial for C2, you did a good job adding sounds and rooms, great!
About the sprites, for me it seems that the bullet spawns from the hand, not from the edge of the gun, the for the gameplay, is impossible to lose, if you stand in the middle of the corridor and don't move, just shoot, Zombies can't get close to you....
I think is a very good job to start practicing, but you need to go further to do a real game!! Keep on