Valve's first-person shooter games are among the most popular on the PC platform, and they include the entire Half-Life series, Team Fortress 2, Portal and both Left 4 Dead and Left 4 Dead 2.
This announcement is no surprise; Valve teased it last week with a series of images mixing Valve properties like Steam and Half-Life's Gordon Freeman in with classic Mac ad mock-ups. What's really cool and unexpected: When you buy a Steam game that's available for both Mac and PC, you're buying a license to the game on both platforms, so if you have a mix of PC and Mac computers in your life, you can play on all your machines.
This month's issue of gaming enthusiast magazine Game Informer also reported that Portal 2 was coming to Mac and that a Steam beta for Mac was imminent. Now Joystiq is reporting that Valve has officially announced its plans.