You already know about the bizarre shift Red Faction Armageddon has made from Guerilla's worthy socialist plot to an "alien invasion". Basically, folks (that's you) seemed to think imposing the story of Das Kapital on a "blowing-stuff-up" shooter held the same socialist fascination as monkey-suited Ed Miliband explaining how he's against cuts whilst in favour of cuts whilst making cross-eyed faces like he's crapping himself, and oh God that BORING voice...

Anyway, I've been tasked specifically with the new multiplayer aspect of that jump, 'Infestation', which pits a fistful of human players against waves of AI attackers. Yes, ladies and gentlemen, it's Horde mode!

Infestation is purely co-op; you and up to three other players choose a map, choose your equipment (more on that later) and then shoot aliens until the victory conditions are achieved. As you go along you unlock both weapons, Nano-Forge abilities, and new levels and modes.

Roje Smith, Armageddon's associate producer, is talking us through the design decisions as we're playing. First off, he explains why they've started from scratch after Guerilla's relatively well-received multiplayer.

"For Armageddon, regardless of mode, we wanted to strongly focus on the story. It's all about humanity's fight to make Mars safe from the creatures that are tearing it apart," he says.

"There is no longer this sense of oppression on Mars with human vs. human conflict; this time, it's all about survival and preventing human extinction by an alien force."

So why a survival mode rather than Left4Dead style PvP? "We decided that our multiplayer should serve as a complementary offering to single player and still put players in a "backs against the wall" survival setting.

"This meant that our multiplayer would have to be a cooperative and story-based experience so each map in Infestation has its own fiction that helps to fill in the gaps from the single player story.  For example, the backstory to the ice levels gives the player better insight into the single player events that take place there."

Moving away from competitive multiplayer sadly meant abandoning much of Guerilla's RPG-heavy multiplayer mode; however, core mechanics of some game modes have transferred, such as Defend incorporating elements of Guerilla's Siege mode.

The standard weaponry from Armageddon's single-player has carried over, so before you enter a mission there's the usual range of pistols, shotguns, assault rifles, sniper rifles, grenade launchers, rocket launchers and so on. However, you can only take a limited selection into a mission, and that includes other special in-game weapons.

"We raise the bar when it comes to our special weapons," says Roje. "Think about the Plasma Beam (like a 100 foot long light saber) or the Singularity Cannon (a black hole that engulfs anything within its radius before it implodes)."

Most notably, the new ammo-free Magnet Gun has carried over, meaning the environment is a weapon as you throw aliens and buildings into each other.  

As importantly players also level up through gameplay, which unlocks more guns, maps, and gives you additional combat options, notably the Nano-Forge abilities (extra-magic superpowers).

Video: Red Faction: Armageddon co-op footage.

"In Infestation, every unlock has a direct effect on how strong your character is, which Nanoforge abilities they can use, how powerful their weapons are and so forth." says Roje.

"It may not have the aesthetic unlocks of Guerilla's multiplayer, but... I think it's safe to say that most players would prefer to have more health and stronger guns than choosing whether they want their new badge to be orange or blue."

The Nano-Forge superpowers are hugely important in multiplayer. Impact is a simple damage attack, which hurts nearby enemies. The Shell ability drops a force-field bubble to deflect projectile attacks and dissolve melee enemies. Shockwave traps your enemies, floating, in a stasis field, leaving them totally vulnerable, which is useful in defense or offense.

The most important Nano-Forge, in my opinion, is repair. "Since the structures in our environments are fully destructible," says Roje, "players will be put into many situations where their cover gets destroyed, leaving them exposed.  Repair can become a life saver." As players can only take one each of these into a mission, selection really needs to be a co-operative process.

We get into an above-ground Defend mission, assigned to defend a tall tower in the middle of a rough sandy area, and quickly understand the challenge. "We force players to juggle priorities and coordinate better teamwork," says Roje.

"It's one thing to have to manage enemies trying to kill you. It's another thing to worry about them trying to kill you AND trying to destroy your defend target.  Instead of simply watching some form of meter trickle down to communicate defend target damage, players will see bits and pieces falling off their defend target." We learn this... Quickly.

That's because these aliens owe a lot to, um, Aliens. They're annoyingly fast, frequently unpredictable and nastily varied, capable of killing you quickly either up close or at range.

The limited ammunition each player carries can leave you highly vulnerable until you find a pick-up, especially as the aliens spawn all around you, which means there's a huge temptation for players to split up to cover the defense of the objectives. We found ourselves running towards critical locations, spaffing our ammo like Blain from Predator, then running away meleeing frantically.

In all the Armageddon modes, as you fight huge chunks of the buildings you're defending get blown away (by both sides) or fall down; if too much is taken down in Defend, it's mission over. Which is where the Repair ability comes in very handy.

We found it helpful to have one player running around inside the building frantically patching up the holes whilst the rest of the team focused on killing the baddies (or running away from them). The level design is a lot more vertical than Gears of War; in fact it's possibly closer to Lost Planet's excellent multiplayer (though the mechs that made that so wonderfully asymettric seem confined to single-player here).

Notably, friendly fire is off, which was a blessing as we were struggling with the speed of the enemies anyway. "It's not only in regards to their speed," says Roje "The ability for most of the enemies to leap in an unpredictable fashion can lead to a LOT of inadvertent friendly fire.  

"Also, with the amount of destruction, having friendly fire turned on would cause players to be more tentative than we'd like.  We want to entertain players, not frustrate them."

There are survival modes as well, which offer a purer Horde experience; kill all the aliens before they kill you. These come in two flavours, normal and the much-harder Dark. In the latter, each player has a short-ranged torch, which gets boosted when near other teammates, combining into a greater light; absolutely necessary for seeing approaching aliens.

"If they don't stick together, then the extremely claustrophobic darkness makes it very difficult to prepare for any potential ambushes," says Roje. "In short, when it comes to the dark levels, the motto is: 'Live together or die alone.'"

Again, our playthrough of survival mode started easily, trying levels out in underground slums and ice caves. However, after a few levels of just firing wildly at the enemies (the only effective weapons you start with are the two grenade launchers), that tactic begins to fail and eventually our last man gets massacred by leaping aliens.

Dropping the difficulty, we ask Roje for tips. "Spamming grenades will only get you so far," he warns. "One of the most important things is which Nano-Forge ability each player has.  

"Unlike single player, where you can eventually wield all 4 abilities at once, we limit each player to one Nano-Forge ability.  If all 4 players want to use the Impact ability, then they can choose to do so.  

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"However, I've learned that it's essential that at least one player has the Shell ability and one player has the Shockwave ability.  The usage of both abilities in unison creates a nice synergy where you're both protected and playing crowd control with the enemies."

Roje's confirmation that "Yes, there will be Steamworks AND Steam Cloud integration for the PC SKU" will certainly lure the PC crowd in for a time, but we're not sure whether this will become a lasting feature on our multi-player cycle alongside Modern Warfare, Team Fortress 2 and Warhawk.

A lot depends on the single-player's reception; if that doesn't do well, players are unlikely to last long enough to try out Infestation. Even if they do, the parallels between Horde mode and this might be too strong to stomach for many players.