But it's not really this that delivers the versatility either - it's the skulls. Once a hidden bonus in Halo 3 for people who wanted to find them and test themselves, now they're put into play in increasingly complex configurations across a Firefight session. They might force you to recoup stamina by melee-attacking enemies, for example, or increase each Covenant unit's strength for a spell, and since Firefight is a potentially endless mode, only limited by how quickly you exhaust your pooled stock of lives (topped up every five waves, when you also receive a new complement of saferoom health-packs), if you're in a group that lasts a long time you could theoretically end up with virtually all the skulls on at once. Bungie uses the introduction of skulls to control pace and tempo, mixing up enemy spawns to keep you on your toes, and you sense that skulls will be the key to Firefight's longevity - and that mixing them up as a bit of 'lite' DLC might not be as out of the question as Jarrard and company suggest.
While Firefight's considered a campaign add-on (with several of the maps unlocked by playing through the main game) rather than a new component of the Halo multiplayer universe, it will get plenty of love on Bungie.net. "What we're doing on B-net is going nuts with statistics," says Jarrard. "Lifetime career stats for all of your Firefights, for medals, for scores - so you and your friends are going to have arcade-style high-score leaderboards for every Firefight map, and we actually built a pseudo ranking system into the website." All this will allow you to compare your skills to other people in various ways. Jarrard reckons the Bungie.net revisions, set to go live with ODST's release, "add a lot more meat" to ODST.
What you shouldn't expect, however, is for ODST to fold into Microsoft's Halo Waypoint project. "Sure we're talking to them, it's just obviously not our project," says Jarrard, diplomatically. "It's really more from a content side right now, we're not talking about feeding them stats or anything like that... It kind of remains to be seen where they're going and what their objective is." Surely their objective is to own Halo, basically? "Yeah, that's probably fair to say. We're pretty comfortable with how we're representing our community on the web, and how we're able to extend our game experience onto the net. With Waypoint it'll be in your living room, so it'll be cool for some things." I'm still suspicious.
Playing with a bunch of randoms without voice communications at PAX, it's hard to get a sense of Firefight's heft, but it's not hard to enjoy. Bunching together for ad hoc co-operation prolongs your more fragile life, and I no doubt win the hearts of my comrades by vanquishing a series of Brutes from my elevated turret position during one particularly fraught wave, even if the post-match score breakdown reveals that the other players are all much better and more experienced than me (probably why they cared enough to queue). It will be interesting to see how the skull variation plays out, what impact the vehicles have on certain maps (warthogs and mongooses have been sighted, although you won't be able to commandeer the Covenant wraiths, for the record), and how long those 10 shipping maps keep Firefight propped up.
My guess would be for a fair while. Bungie's deliciously indiscreet developers let slip at a fan panel on Friday that the campaign takes around eight hours to finish even if you only uncover a few of its extras and secrets, and while together with Firefight this may not be a game with content bulk to match some of last year's fourth-quarter monsters like Far Cry 2 and Fallout 3, the hopefully not-so-distant promise of Halo: Reach beta access and the second disc of Halo 3 multiplayer content (including three maps that haven't made it into previous download bundles) patch this up to a strong standing. Which is a good thing, because whatever the plan was and whatever it is now, hopes for ODST are as big as the game was clearly always going to be.
Halo 3: ODST is due out on 22nd September for Xbox 360.