I like the idea, fits the theme perfectly, and it was quite fun. A few points to note (a few of them have been noted by others already): - The zombies are too detailed compared to the other objects, they look out of place in comparison - Getting attacked really needs some sort of feedback, either a sound effect or something like a red flashing screen, first playthrough I did without noticing that I was being attacked - Some zombies liked to get stuck in the ammo-building - Personally I feel like it would have been better to switch between top down/fist person view with a keybind; when I spotted zombies at the other side of the tent in top down view I had to walk further then really necessary to be able to shoot them accurately - As a plus-point, the rectangle that others asked for earlier was added, which helped with aiming
Overall good idea, maybe not perfect, but still well done :D