Challenge what? My ability to tolerate pointless looting coupled with anti-social teenage douchebaggery? This game has no complex element of social interaction because there is no real penalty for killing another player. I was expecting a Left 4 Dead style game with a focus on simulation rather than action. Sadly, I am disappointed as to how shallow this game truly is. Once you get a weapon the zombies aren't that much of a problem. It's all PVP deathmatch nonsense. To be honest, I expected this game had so many players because it actually offered some amazing gameplay that has never before been seen. This games popularity can explained very simply. Zombies, scarcity, and looting. For some reason people love games where they get to open endless amounts of presents. WHO KNOWS WHAT INSIDE? A gun or some scrap metal? OOOOO... Maybe it's something you need, MAYBE IT ISN'T. Very complex and thought provoking! It taps into that simple animal mind that every ape has. Wake me up when this game actually captures the complex social/military dynamics of an apocalyptic scenario. There is a bit more to it than just shoot whoever has stuff.