The PC edition of Halo: Spartan Assault has up until now been exclusive to Windows 8 as it's only appeared in the Windows Store. But that is about to change as the game hits Steam on April 5 - a version of the game that's compatible with Windows 8, Windows 7 and Windows Vista.
A twin-stick shooter, Halo: Spartan Assault is also available on Windows Phone 8, Xbox 360 and Xbox One.