A slightly modified version of State of Decay has been resubmitted to the Australian Classification Board, Undead Labs has announced.

The game was refused classification for its explicit drug use, namely the player characters’ use of stimulants. These have now been relabelled “supplements”.

“Who could possibly not like vitamins?” Undead Labs asked.

“They're good for you. Anyway, we're feeling pretty optimistic about our chances.”

The developer mentioned it was still waiting to hear what was happening with the game's New Zealand version, which received an R18 rating for “Graphic Violence and Offensive Language”.

Undead Labs also announced that co-op in State of Decay wouldn’t be implemented for a while yet.

Co-op multiplayer was initially planned for the game but dropped more than a year ago for technical reasons.

“We were up to our eyeballs trying to retrofit our game engine to support an open-world sandbox game rather than the FPS style games it had been designed for,” said Undead on its official forum.

“That retrofitting would have extended to the multiplayer support as well, and we estimated it could have delayed release of the game by as much as half a year. It was a painful decision, but a necessary one given the realities of our team size and project budget.”

However, now that the game has done well, co-op is back on the cards.

“We now have the opportunity to realize some of our hopes – and your hopes – for how we reinvest in the game and make it even better,” said Undead Labs.

“We know co-op is the most requested addition to State of Decay, and we've also continued to hope it might be a possibility after release.

“Unfortunately, after reevaluating it over the past few weeks, we believe our original estimate of six months was optimistic; the actual time is probably closer to nine months.”

Shoehorning the mode in before that wouldn’t make for a great experience, said the studio.

However, multiplayer would be “the absolute heart” of any future State of Decay games, it added.