While it's only been out since June 5, Undead Labs' zombie survival title State of Decay has already sold 550,000 copies. That's enough to earn it the distinct honor of being the "fastest-selling original game ever on Xbox Live Arcade." Rough around the edges, sure, but folks seem to be digging it. Need I remind that a PC version is still on the cards? High fives all around.

"Fortunately [the Steam version] been in development alongside the Xbox 360 version since Day 1, so we just need to integrate with the Steam platform and add native support for keyboard and mouse control," says Undead. "We'll also continue to issue Title Updates at a fast pace to refine game balance and fix bugs."

There's a sandbox mode "designed to be a pure survival simulation" in the State of Decay pipeline as well. Sound good? Think I'm going to hold out for this on PC.