http://www.macnn.com/articles/10/05/26/episode.one.and.episode.two.also.added/
Half-Life 2 arrives on Steam for Mac
updated 06:50 pm EDT, Wed May 26, 2010
Episode One and Episode Two also added
Valve on Wednesday added several new titles, including Half-Life 2, to the Steam gaming service on Mac or Windows platforms.. The company also added two earlier versions of the game, Half Life: Episode One and Episode Two.
Each of the titles features cross-platform support for Steam Cloud, allowing users to play for free on either platform after making one initial purchase. The service also saves games to the cloud, enabling the game to be continued even when switching between platforms.
Valve is currently running a limited-time promotion that drops the price of the Half-Life 2 titles by 30 percent.
