At first I thought it was a James Veitch reference lol (Lockdown-The game!). Graphics were good, maybe you can tweak sfx a bit, and also give the player some movement animation (the shotgun recoil was a nice bonus), Maybe you can implement some sort of a wave system? and maybe player can find some sort vaccine to heal back? I was coughing all the time, viruses were everywere! And also maybe you can use the shotgun's bullets to your advantage and make it deal more damage at close combat? Good job!