Steam News has word that the launch of the Mac client for Steam continues with the release of another dozen games for the Mac audience, include the first three titles to support cross-platform play with Windows users, which are Killing Floor, Altitude, and Madballs in Babo: Invasion. Word is: "To celebrate the launch of these titles, Killing Floor will be offered at 33% off its regular price (for a limited time). An Altitude Free Weekend promotion is available now on Steam, and those who wish to purchase the game and play beyond the weekend may pick it up at 50% off its regular price. And Madballs in Babo: Invasion is also available at 50% off its regular price." This page offers the complete list of all the new Mac titles on Steam.