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Games that allow some modes of crossplatform multiplayer but not others, or those that have some interoperable as well as non-interoperable platform versions. (For instance, PC and Mac versions of some games are cross-platform compatible with each other, but iOS, Android, and Xbox 360 versions are often not compatible either with each other or desktop versions.

The latest iteration of Sid Meier's famous strategy game series doesn't get listed on most sites as being a cooperative game, but that's only because how most alliances are temporary. That certainly doesn't need to stop you from getting together online with a few friends to beat up on the AI (or try to) before turning on each other!

Built from the ground up for cooperative play and supporting OSX, Linux, and Windows, Left 4 Dead 2 definitely belongs on this list. And for a short time during the holidays in 2013, Steam offers the game for free!

In December 2013 the publisher confirmed that ESO will be coming to Mac OS X as well as to Windows. The expected release date is April 4, 2014. The MMO RPG based on the Elder Scrolls universe will use a subscription model, like World of Warcraft (also available on OS X). Exact specs aren't out yet; the systems we list here are guesses. Console versions for PS4 and Xbox One will follow in June 2014.

Markus "Notch" Persson created this block-based game in 2009 using Java. Years later, versions exist for PC, OSX, iOS, Android, and Xbox, with a PlayStation version in the works.