 Valve was interested in the game, they were looking for a "low risk, low cost" third-party game to test on Steam; it became the first non-Valve game to be released on the platform in October 2005.Also in 2005 whilst at Lionhead, the co-founders were working a game called "The Room" using clay tubes and portals.In retrospect, the founders noted it had similarities 2007's "Portal".