Fun game, but actually really easy. Just spam as many bullets as possible on the first level so your barricade doesn't take too much damage and then just look for survivors. More survivors = easier levels, and less time spent repairing. Once you find the first automatic weapon it's all downhill from there. Spam bullets and use your backup weapon to pick off runners/zombies destroying your barricade. The hunting rifle is overpowered and kills everything in one hit.