State of Decay developer Undead Labs has signed a multi-year, multi-title agreement with Microsoft Studios, founder Jeff Strain announced on the studio's official blog.

Strain notes that more details on the agreement will be shared later this year, as the developers "think it's best if we just keep our heads down and build some prototypes before we talk too much."

He also added that there are "big things" coming up for its zombie survival sandbox title State of Decay, which launched last June and became the fastest selling Xbox Live Arcade title in history. The game sold 250,000 copies in two days and 500,000 copies in under two weeks.

"It's been a long haul from the original vision to this point, and the road ahead of us will take years to travel," Strain wrote. "We hope you're up for the trip, because we can't do it without you."

Undead Labs has had another title in the conceptual phase, codenamed Class4, for some time. Class4 will be a "shared virtual world" that will be a follow-up of sorts to State of Decay and build on the experience created in the studio's first title. Undead Labs has said any future sequels to State of Decay would likely come to next-gen.