Valve has announced that they will be releasing Steam for Mac in April. Left 4 Dead 2, Team Fortress 2, Counter-Strike, Portal, and the Half-Life series will be available at launch.

Along with the announcement of Mac versions of the above games, they’ve also announced Steam Play, which will allow customers who purchase any or all of the above games for Windows or Mac to play on the other platform for no extra charge. So for example, if you’ve purchased Half-Life 2 for Windows you’ll be able to download and play it on your Mac at no charge. Mac and Windows players will also be able to play online multi-player with each other, sharing servers, lobbies, etc.

Valve says that Portal 2 will be the first simultaneous release for Mac and Windows and will be released this holiday season.

Josh Weier, Portal 2 Project Lead:

Checking in code produces a PC build and Mac build at the same time, automatically, so the two platforms are perfectly in lock-step. We’re always playing a native version on the Mac right alongside the PC. This makes it very easy for us and for anyone using Source to do game development for the Mac.

I’m very excited for the release but even more excited about the future of Mac gaming. The ability for developers to check in code that produces PC and Mac builds automatically is a big deal.

Image credit to Joystiq.