E3: Left 4 Dead 2

The result, to be perfectly honest, is more of an expansion pack than a full-blown sequel, although we can't imagine any of the legion fans of this blistering, definitive co-op shooter will mind in the slightest. Left 4 Dead 2 presents five complete new campaigns starring four new characters, and transposes the action to a poignantly ruined New Orleans. It adds melee weapons, reworked guns and new ammo, and one new boss enemy type. That's your lot.

(Update: No it isn't! Although Erik Johnson was quite matter-of-fact with us about the game's limits, he missed a few things out. His colleague Chet Faliszek has been forthcoming elsewhere, discussing gauntlet moments - where players are thrown through a relentless onslaught of zombies in close quarters, such as on a narrow bridge - and the Wandering Witch, who stumbles around in a daze, making her harder to avoid. There's also a hazmat-wearing basic Infected, limb loss, and unannounced extra boss enemies and a new game mode, while the AI director should have more control over level layouts and weather this time. Apologies for not including these details originally - blame lack of sleep.)

It's easy enough to see Valve's reasoning, however. If it ain't broke, don't go back to the workshop for three years to fix it; iterate fast instead, churn out the content, and feed the rabidly hungry mouths presented by the audience of any hot multiplayer game before they turn away. In a way, it suits the immediacy of Left 4 Dead to be followed up so fast - and the result is every bit as compelling.

The four new survivors are white-suited playboy Nick, tough girl Rochelle, burly Coach and wiry Ellis. I didn't, frankly, dwell on their characters and back-stories, choosing to plunge straight into a run through a campaign called The Parish with three other players that ended ignominiously about half an hour in. Anyway, it's the city that's the star of Left 4 Dead 2. New Orleans' sultry atmosphere and crumbling decadence are captured perfectly through the rubble, brightly lit with washes of hazy, late-afternoon Louisiana sun. It's gorgeous.

The Parish leads you from seedy docks, through veranda-decked French Quarter back-streets, and into manicured parks. We're promised a broad range of other environments from the region (one of them surely has to be the bayou). The game looked considerably better on PC, although the resolution of Valve's ridiculously expansive monitors probably accounted for some of that. Overlaid, directional, on-screen prompts guide you to weapon and ammo pick-ups, and following them introduces the reworked guns - all with an improvised, lashed-together feel, but packing a big kick - and also the melee weapons and incendiary ammo.

Melee weapons are powerful, temporary items - the examples to date are an axe and the famous frying pan from the trailer - that incapacitate your two guns while you hold them, and prove very useful when dealing with the sudden, overwhelming flash-mobs of mauling infected of which our AI director seemed inordinately fond. Incendiary ammo adds a fire effect that can spread from zombie to zombie and is also useful against crowds, but is probably better employed at range, for obvious reasons.

New enemy the Charger made a big impact; bulky, but incredibly fast, this American football-inspired monster will pick a target out of the four of you, run you down and then straightforwardly but powerfully beat you up. Co-op technique with these guys is mostly a matter of keeping a watch for their possible arrival from all quarters - some areas are terrifyingly open - and organising focused fire quickly to take them down. Smokers seemed a little more devious than before, too, lashing their tongues around obstacles like complex pulley systems to keep themselves out of obvious lines of fire.

Otherwise, the relentless pace, unforced co-op dynamics and constant tension and surprise for which Left 4 Dead is justly celebrated are all present and correct. Like its infected hordes, this one's an absolute no-brainer, even if the people making it are very far from that. Read on for an interview with Valve's Erik Johnson to find out why the made it now, why exclusively on 360, and more.

Eurogamer: New Orleans is a cool setting, but it strikes me as a little bit risky - considering what that city suffered with Hurricane Katrina and its aftermath, with all the looting - setting a post-apocalyptic survival game there.

Erik Johnson: I think with things like that, it's kind of how you're dealing with it. But we chose New Orleans because of how cool of a city it is. We have people at Valve who grew up in New Orleans, we think the culture and the music is really cool, the architecture is beautiful. It makes a great setting for a spooky type of game.

To be honest, the Katrina thing wasn't... I think where you get into trouble is when you're being insensitive, when you're trying to use something like Katrina that happened and was really terrible as a way to present the game. Hopefully it doesn't come off as insensitive.

Eurogamer: It seems quite soon to be bringing out a sequel for Left 4 Dead. It was Valve's big game last year and it's going to be the next. Why did you choose to do that?

Erik Johnson: Well, you know, we've had lots of successful game and taken different tacks in terms of what we were going to go build. We spend a lot of effort on the game design side and the business side, it involves everything we do, trying to figure out the optimal way to deliver content to customers.

It felt like - co-op was a new thing for us, and we learned a lot, the most we've ever done about a type of game, shipping Left 4 Dead 1, and we wanted to build on that. And the team was really efficient at building that kind of product and getting it out.

Eurogamer: Will you be extending the SDK support from the first game to include Left 4 Dead 2?

Erik Johnson: Yep, we love people making mods and putting their own spin on our technology, so as much as we can do on that, we will.

Eurogamer: The Xbox 360 exclusivity - was that a business decision, an arrangement with Microsoft? Or was it down to your preference for the Xbox platform?

Erik Johnson: We don't have a ton of experience internally building products for other console platforms. Left 4 Dead 1 was PC and Xbox, so it made a lot of sense to go for Xbox this time.

Eurogamer: Valve is known for its continuing support of its PC games, the way you've handled Team Fortress 2, the way you support games through Steam... how have you found supporting an online multiplayer game like Left 4 Dead through Xbox Live? It must be a different experience.

Erik Johnson: It's harder. Absolutely it's harder. In the same way that we put a lot of effort into making internal development efficient, we want as much as efficiency as possible from people building games to the customers experiencing it. On the PC that's much easier of course, on the 360 it's just not.

Eurogamer: Because you're in control of the update process on PC?

Erik Johnson: Yeah, and not just the update process but kind of everything. We know that every PC has a hard drive for example. We can't guarantee that on 360. We can allow ourselves to take iterative game design risks, because we know that if it doesn't work in the wild - the things that are difficult to test internally that require scale - that we can ship that to customers, say in Team Fortress 2, and if it doesn't work out we can change it back pretty easily. Customers kind of enjoy being part of that process. We're not afraid to make mistakes.

Eurogamer: Are you going to continue to support the first game with more DLC and patches, or is the emphasis now on Left 4 Dead 2?

Erik Johnson: We're going to keep building stuff for Left 4 Dead 1. We'll support both. We've always felt that it makes good business sense to keep customers happy. It'll be good for Left 4 Dead 2 to support Left 4 Dead 1. We do have risks in that we don't want to split the two camps, we don't want a Left 4 Dead 1 group and a Left 4 Dead 2 group, that's a problem that we need to figure out.