Eh, not bad.
Not bad I suppose, but it feels kinda too simplistic. Certain elements of the game don't seem to make sense. Like, why he wouldn't run away for an example. It'd probably make a lot more sense if you had him cornered, like placed a wall behind him or something. That would put a lot more emphasis on the whole "trapped" feeling that this game may have slightly given off.
I also didn't really like how you had to click on the zombies in order for your bullets to hit them. Considering that this is a side-view type game, it'd probably make a bit more sense if the bullets hit the zombies regardless. But I did like how the zombies were easy to shoot, as in the hitboxes weren't too big or too small, and the zombies didn't move at lightening speed.
I did really like the art though, even though it was black and you couldn't see anything. It really worked and gave off a creepy feeling. Well done on that note, but on gameplay and stuff, eh, a bit of improvement would be suggested.