A strange fog rise up. You grabbed your shotgun when you heard a voice outside. Wtf Zombies. Try to stay alive for 5 minutes and kill them all to win and unlock next difficulty level.
The endless mode was changed to difficulty levels (easy, medium, hard, very hard, hell on earth, impossible). You start in easy mode. Surviving for 5 minutes and kill all so far spawned zombies to unlock next level.
