Microsoft's plans for the launch of Windows 8 later this year apparently include offering some exclusive games as well. Rock Paper Shotgun reports that for the upcoming launch of the turn-based strategy game Skulls of the Shogun, developer 17-Bit Studios will make the PC version of the game a Windows 8 exclusive.
In other words, it won't be available for Windows XP, Vista or 7 (it will also be launched for Windows Phone and for the Xbox 360).

Asked why the development team made the game a Windows 8 exclusive for the PC, Skulls of the Shogun's designer and programmer Borut Pfeifer stated:

Working with MS, we were all really excited about the cross-platform nature of the game (itís a great fit for mouse, touch, and gamepad, which is rare). We had a choice to support either Windows 8 or GFWL on Windows 7.