One of the big promises that came out of Microsoft's Build conference this year were apps that'd work across a number of Windows devices with a single purchase, and Redmond is using Halo to lead that charge. The first group of applications includes Halo: Spartan Assault and Skulls of the Shogun, both of which recently made the conversion to universal games -- making them playable across Windows Phone, Windows 8 and RT devices for one price. If you'd rather not pay for your entertainment, though, Microsoft also converted the likes of Wordament, Minesweeper and Hexic too. However, as Windows Phone Central notes, buying the universal version of Skulls doesn't grant access to the Xbox 360 version, nor does Spartan Assault's universal purchase unlock the Xbox 360 or Xbox One versions. Given that the Xbox division is still pretty separate from everything else though, that isn't exactly surprising.