Valve plans to release the critically acclaimed Darwinia to gamers worldwide via its Steam service. The game will be available from December 14 and will set you back the bargain fee of $19.95. Darwinia joins Rag Doll Kung Fu in a growing line-up of non-Valve titles appearing on Steam.

"In today's market, it's incredibly difficult for an independent developer to secure worldwide distribution for a new property, let alone for one that attempts to blend genres and offer a wide variety of gameplay styles," said Vicky Arundel at Introversion. "Through Steam, however, we are able to offer Darwinia to millions of gamers and early adopters the world over."

"After playing the game around the office, there didn't seem to be a reason why a game as great as Darwinia wasn't available to gamers worldwide," said Valve's Doug Lombardi. "When everyone gets their chance to play it, we think they'll be staying up all night protecting Darwinians just like us."