Here's the less obvious big departure with Halo: Spartan Assault: it's the first Halo game in history that has a female protagonist. She's Sarah Palmer, the pouting Sergeant Apone wannabe from Halo 4's Spartan Ops campaign, and she's here to kick Covenant arse and take names in commute-friendly, five to 10 minute bursts of top-down blasting. OK, so it's not quite giving anybody the right to vote, but it's nice to know that mass-murdering alien scum isn't exclusively the province of the chromosome-deficient.
The bigger innovation with Spartan Assault is that it's the first Halo title for a mobile platform - specifically, Windows 8 smartphones and tablets - created in partnership with Vanguard Games. That puts it a little beyond our editorial jurisdiction, of course, but there's the pressing suspicion that the game will turn up at some point on Xbox One, which features a modified Windows 8 OS.
343's Dan Ayoub won't confirm anything of the sort when I ask about it, but there is crossover already in the shape of additional achievements, emblems and XP for Halo 4, and 343 intends to patch in Xbox 360 controller support for Windows 8 PCs. The story reinforces the overlap: it's all played out on a mission simulator aboard the UNSC Infinity, setting for Halo 4's multiplayer. Even if Spartan Assault doesn't come to a home-format Xbox, it's clearly aimed at people who own one.
Comprising 25 missions (with more potentially to follow as DLC) strewn across the surface of yet another hotly contested UNSC planet, the game is an elegant abbreviation of Halo's sandbox principles that also attempts to conquer one of the more lingering problems with twin-stick shooters on touchscreen - the absence of actual, physical sticks.
Hitherto, it's been common to find your thumb drifting accidentally away from the virtual stick as you play. 343 and Vanguard have put together an adaptive control scheme that compensates for the drift, repositioning the virtual sticks and recalculating the centre of the movement arc. I won't pretend to understand how all this works, but it's undeniably impressive - my thumbs jerk around during hands-on time without throwing Palmer off. The lack of a physical break between touchscreen and bezel still poses difficulties, but that's an issue with the device, not the game.
The basics are very familiar - indeed, the screens should tell you everything you need to know. Players direct a hail of fire with one stick and move with the other, hurling grenades, switching guns and performing abilities or context sensitive actions via fat, holographic buttons down the right hand side. Melee attacks are performed by tapping anywhere. The handling is a little sticky in places, such as when entering and leaving a turret, but I'm assured that's a kink the developers will iron out by release.
Firing up an introductory sweep-and-clear mission, I spend a few moments in the company of a pair of SMGs, before swapping to a UNSC shotgun whose limited range is all the more palpable for the camera angle. Plasma pistols can be charged up by holding the fire button, and the Battle Rifle offers its usual, trustworthy blend of power and range. The vehicles I've sampled are no less closely modelled on their big screen brethren, though there's currently no provision for aerial combat. The Wraith Tank is as fatally ponderous as ever, its main gun swivelling independently of its body, and crumples gorgeously under artillery fire.
Halo's eccentric physics and pliable AI systems aren't quite as conspicuous here, thanks to the limits of the mission design and hardware, but a respectable selection of variables have been brought across from the main games, such as Grunts turning kamikaze and Elites going postal once you've chewed away their shielding.