I also got like 50 something kills and it went dark. I wish I could see the bullets or some kind of target reticle, I was just kind of holding down the button and clicking randomly to move around the scene. It was kind of hard to tell the walls were closing in on me. Maybe some more geometry or something that showed that it was a small world, and not just walls closing in on me with zombies. Maybe giant lego enemies or something to give the feel of it being a small world.