The latest game to sign up for Steam, Valve's proprietary digital delivery service for the PC, is Introversion Software's Darwinia. The cult strategy action title, produced by Introversion's small UK-based development team and an entrant in this year's Independent Games Festival, will be download-exclusive to Steam when it debuts on the service on December 14. As a result, Introversion will remove links to its own digital-purchase option for Darwinia, as well as temporarily disabling the downloadable demo at Valve's request. Those wishing to purchase the game directly from Introversion will still be able to get a boxed copy containing both Windows and Linux versions for 19.99 UK pounds ($34.35 USD). In the meantime, those who pre-order the game on Steam starting at the beginning of December will receive a 10% discount on the $19.99 purchase price, along with a special making-of video. This move is the latest in Steam's recent expansion into non-Valve-developed product distribution via its content delivery system - titles either being sold or to be sold via Steam include Rag Doll Kung Fu, Narbacular Drop, They Hunger: Lost Souls, Pirates Of The Burning Sea, and SiN Episodes. Other similar efforts include EA's similar move into digital downloading, albeit solely for its own games, and the extensive digital game content available for free and pay-download on Microsoft's Xbox 360. "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, head of marketing at Introversion. “Through Steam, however, we are able to offer Darwinia to millions of gamers and early adopters the world over."