Valve has stopped with the teasing and has officially announced that its online gaming service Steam is coming to the Mac. As a bonus, the company also plans to make the Mac a "tier-1" platform, promising simultaneous release of games on Mac OS X, Windows, and Xbox 360.

Valve has developed a Mac-native version of its Source engine, using the cross-platform OpenGL. "We looked at a variety of methods to get our games onto the Mac and in the end decided to go with native versions rather than emulation," John Cook, Director of Steam Development, said in a statement. "The inclusion of WebKit into Steam, and of OpenGL into Source gives us a lot of flexibility in how we move these technologies forward."

Beginning in April, Mac users will be able to access games via Steam, including Left 4 Dead 2, Team Fortress 2, Counter-Strike, Portal, and the Half-Life series. The Mac Steam client is based on the latest version for Windows that is currently in beta, which is where the first hints of Mac OS X compatibility were discovered.

That version includes a new Steam Play API that will allow users to access and play games from either a Windows PC or a Mac. Progress on one platform is automatically updated and synced when using the other, meaning all the fragging you do on your work PC (on your lunch break, of course) will be reflected when you log in from your Mac at home. Playing games on either platform won't cost extra.

The Mac compatibility extends beyond Steam Play, however. All future games, beginning with Portal 2, will be available for the Mac the same day as the Windows version. "We are treating the Mac as a tier-1 platform so all of our future games will release simultaneously on Windows, Mac, and the Xbox 360," Cook said. Players on all platforms will be able to play each other in online multiplayer setups, as well. "We fully support a heterogeneous mix of servers and clients."

These announcements are surely music to Mac gamers' ears. Besides Steam and Valve's own titles, making Source cross-platform also means other developers using Valve's engine can easily create Mac-compatible versions of games without much additional effort.