Microsoft Studios, 343 Industries and Vanguard Games have released Halo: Spartan Strike today on a number of Windows based devices including Windows Phone 8/8.1 and iOS.
Weighing in at $5.99 (or $9.99 for the bundle of Halo: Spartan Assault and Halo: Spartan Strike on Steam)
Halo: Spartan Strike is set during the events of Halo 2 on New Mombasa in 2552. As a Spartan in a classified ONI simulation, there are 30 missions leading UNSC troops through cities and jungles with an arsenal of weapons, abilities and vehicles.
There is no word on if/when this will come to Xbox but playing the game has its own achievements and unlocks an exclusive emblem, nameplate and avatar in Halo: The Master Chief Collection on Xbox One.
You can download Halo: Spartan Strike from the following locations