So far Portal is the only title currently playable on the closed beta, but native Mac versions of Left 4 Dead, Left 4 Dead 2, Team Fortress 2, Counter-Strike and the Half-Life series have been announced. Moreover future titles from Valve, starting with Portal 2, will see a simultaneous release for both Mac and Windows systems. The company will also add a feature called Steam Play that will let gamers play any of these titles on either platform at no extra cost.
Valve has already begun licensing Mac versions of its Source engine and its Steamworks social suite, but has not yet named any partner companies or said whether any of them will outfit their games with Steam Play.
In other Mac-gaming news, Blizzard has just released a beta version of the upcoming StarCraft II for the platform. Players can snag the test release for free at Battle.net, but they must already be in the beta test program to get it.