The "Halo" series might be most closely associated with the three Xbox consoles, but it has a long history of dabbling with other platforms before the recent iOS debut of "Halo: Spartan Strike" and "Spartan Assault."
In fact, it wasn't until "Halo 3" in 2007 that the franchise was locked down as an Xbox console exclusive, a status then retained for seven years on the trot.
Series opener "Halo: Combat Evolved" was at concept a Mac and Windows game, and though it debuted on Xbox in 2001 as a hugely successful system-seller, it arrived on the two computer platforms by 2003's end.
And while Mac was dropped for "Halo 2," Microsoft's own Windows OS retained a slice of the pie, albeit 2.5 years after the Xbox game first arrived.
It took another 11 years to return to Apple platforms with a double release of "Halo: Spartan Assault" and "Halo: Spartan Strike" on iOS.
Outside of games, universe-expanding novelizations had been available since "Halo" began, but the games' rising value led to more extravagant marketing budgets and a number of other transmedia exercises.
For example, "Halo 2" viral marketing campaign "I Love Bees" became legendary, setting up a chase to track down public payphones and receive calls at predetermined times.
More widespread were live-action shorts preceding "Halo 3" (2007), "Halo 3: ODST" (2009) and "Reach" (2010) as well as the latter's anime project "Halo Legends."
Those built a platform for a more ambitious "Halo 4" campaign in 2012: miniseries "Forward Until Dawn" was a webisodic sci-fi drama, and Ridley Scott-produced "Halo: Nightfall" helped push remastering effort "Halo: The Master Chief Collection" in 2014.
But 2013's "Halo: Spartan Assault" was the most radical departure, swapping first-person perspective for a very different top-down, twin-stick style far better suited to lower-powered devices, and given six months' exclusivity on Windows Phones and the Windows 8 Store before migrating to Xbox One and then the older Xbox 360.
Though follow-up "Halo: Spartan Strike" was delayed from December 2014 to April 2015, it now looks like provident timing, ensuring a day-and-date release across the Windows Store, Windows Phone, and iOS, available separately or in a bundle together with its predecessor.
Following iOS versions of Office and Outlook, the "Halo: Spartan" titles reinforce a different Microsoft approach that sees the tech giant look for opportunities on rival mobile platforms as well as its own.