It's a interesting concept. But, and I mean a big but, you need to fix these bug ASAP (as mentioned in the comments below): the camera FOV seems to big a bit to big, it feels like I'm always zoomed in. Some zombies seem to not die no matter the amount of bullets you shoot at them! After I have killed the needed amount of zombies, I just didn't know where to go or what to do, the text (I'm assuming) telling me what to do, dissapeared very quickly. I suggest just keeping the objective on the screen at all times. Aside from that, the game is fun and you did a good job, keep improving it! :)