If you're a fan of tactical shooters, get yourself over to Steam to take advantage of the weekend sale on The Bureau: XCOM Declassified (available for OS X and Windows). It's 75 percent off this weekend - normally $49.99, you can pick it up now for $12.49. This marks the Mac debut of The Bureau on Steam - the game was already released on the Mac App Store.
The XCOM series dates back to the mid-1990s, in which you're a member of a clandestine government organization focused on repelling an alien invasion of earth. The XCOM series went dormant in the early oughts, and was revived in 2012 with the release of XCOM: Enemy Unknown and an expansion pack, XCOM: Enemy Within.
The Bureau is the second major XCOM game to be released with the rebooted series; it's 1962, at the height of the Cold War between the U.S. and the Soviet Union. XCOM, originally created to help prevent a Soviet invasion of the United States, suddenly finds itself at the epicenter of an alien invasion.
The game is a third-person shooter with tactical elements that require you to command additional agents with special skills. It's built on Epic's Unreal Engine 3 and was ported to the Mac by Transgaming.