Kill enough zombies all while completing quests allows you to level up like previous games as well. (gamingnexus.com)
It maintains meaning by still allowing you to level up, presenting challenges and holding off specific challenges until you've killed enough zombies, often in the thousands. (justpushstart.com)
There are never enough zombies in the world, and Dead Island is set to to throw even more of those shuffling bastards at us. (wolfsgamingblog.com)