"Run away" hit State of Decay has reached sales of one million units across Xbox Live Arcade and Steam Early Access. The game reached the half-million sales mark within a few weeks of its June 5 launch on XBLA.

State of Decay: Breakdown, the first expansion for the zombie survival simulator, has been delivered to Microsoft for "pre-certification testing." The team at Undead Labs hopes to have feedback and officially submit the expansion by the end of next week.

"Assuming no catastrophes, we plan on getting Breakdown into your hands by the end of October," wrote Undead Labs' founder, Jeff Strain, on the company's blog.

State of Decay is expected to exit early access status on PC by the end of the year.

This article was originally published on Joystiq.