Btw, when it comes to replayability, what I would like to see in this game is some emergent gameplay. Some random chance events/quests, like getting a recorded signal on a radio of a nearby stranded person (that will have conveniently become a zombie since we don't have npcs) while strolling through a town, getting an SOS and spawning a mini-POI at runtime (if that is possible) of a crashed helicopter/whatever, players triggering BM-like hordes by setting off a POIs alarm system, reduced trader supplies if players don't kill enough horde zombies, a random chance for an air supply if the player kills many zombies within an area, extreme local weather effects that the player has to run from or take cover on the fly (acid rain, blizzards, rad sandstorms) etc etc.