After a string of artsy teases through Apple-styled imagery, Valve today announced that it is extending Steam support over to the Mac. This marks a significant achievement, making Steam the first major digital distribution platform to bridge the gap between Windows and Mac operating systems.

Set to launch this April, Valve’s library of games including Left 4 Dead 2, Team Fortress 2, Counter-Strike, Portal, and the Half-Life series will be among the initial offerings. Going forward, Valve is treating the Mac as a tier-one platform, meaning that all future titles will release simultaneously on Windows, Xbox 360, and PC. Portal 2 will kickstart this commitment.

Seeing as Valve’s in-house middleware Source now supports Mac as a target platform, this also has the intended side-effect of making it easier for third-party developers to port any Source-powered offerings over to Mac. Not to mention, it gives Source quite a selling point over that of competing engines.

“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,” said John Cook, Director of Steam Development. “The inclusion of WebKit into Steam, and of OpenGL into Source gives us a lot of flexibility in how we move these technologies forward. 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. Updates for the Mac will be available simultaneously with the Windows updates. Furthermore, Mac and Windows players will be part of the same multiplayer universe, sharing servers, lobbies, and so forth. We fully support a heterogeneous mix of servers and clients. The first Mac Steam client will be the new generation currently in beta testing on Windows.”

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