March 8, 2010 - Valve announced today it will bring Steam, Valve's gaming service, and Source, Valve's gaming engine, to the Mac. Steam and Valve's library of games including Left 4 Dead 2, Team Fortress 2, Counter-Strike, Portal, and the Half-Life series will be available in April. "As we transition from entertainment as a product to entertainment as a service, customers and developers nee... more.