Darwinia and Defcon developer Introversion stopped working on Subversion nearly a year ago, Eurogamer has discovered.

Subversion resembled a collection of tech demos but "the core game itself wasn't really that great", creator Chris Delay told us.

"What happened was, we were tinkering away on Subversion for ages and ages, trying to make some progress - and we did make a lot of progress on it - but we always had this worry that the core game itself wasn't really that great. There wasn't really much to do.

"We had literally years of tech demos but no sort of cohesive core game. It's the core game that was missing.

"Whenever we stopped and thought about it from a high-level point of view, in terms of what's the player going to be doing, where's the fun going to come from, we were drawing a bit of a blank, all the time.

"We finally faced up to it," he said.

Subversion, an infiltration and espionage game where gamers controlled a team of operatives moving through hostile high security buildings, is officially now on hold.

Darwinia developer Introversion has announced a new game called Prison Architect.

In it, you "build and manage a maximum security prison", Introversion's creative mind Chris Delay told Rock Paper Shotgun.

No other Prison Architect details were offered.

Subversion, Introversion's other project, is on hold.

Introversion won worldwide acclaim with strategy game Darwinia. Defcon, Multiwinia and ill-fated XBLA project Darwinia+ followed.

Video: Subversion.

Couple Darwinia+'s longer than expected development with a "poor performance" on Xbox Live Arcade, and it's no wonder Introversion has decided to focus its future on Steam.

"Do we regret working with Microsoft? No, but it's unlikely we'll work with them again," Introversion's mouthpiece Mark Morris told PC Gamer.

"[Microsoft] make you work harder on the production value, but they don't back it up with sales."

Darwinia+ is a combination of Darwinia and Multiwinia - a project bossed by Microsoft that took Introversion down a frustratingly long and winding development path. Darwinia+ was eventually released in February 2010, nearly four years after Darwinia - and a precocious, naive Introversion - won top honours at the Independent Games Festival.

The poor sales of Darwinia+ almost ruined a fragile Introversion. What saved the once bastion of British independent gaming was, coincidentally, Steam, and the sale of nuclear warfare strategy game Defcon.

"For the first time in a long time we've got a cash flow that extends out for two years at our size, which is nice," said Morris in August 2010.

With that cash, Introversion can hoist its sails; and with creator Chris Delay reinvigorated to be finally working on his beloved Subversion - comes the wind to fill them.

Video: Subversion: Introversion's long-awaited 'next'.