Back 4 Blood details its deck-building card system in latest trailer

Back 4 Blood isn't shying away from comparisons to co-operative zombie FPS classic Left 4 Dead - developer Turtle Rock Studios is responsible for both, after all - but the team is aiming to deliver more than a carbon copy of its earlier game. And one of its innovations comes in the form of an intriguing deck-building card system, which it's now detailed in its latest trailer.

Borrowing one of Left 4 Dead's most innovative features - an AI-driven Game Director - Back 4 Blood works behind the scenes to monitor players' "health, actions, and choices", and responds by, as Turtle Rock puts it, "choreographing the world around them".

However, judging by the game's new trailer, Back 4 Blood's Director is able to pull from a much wider set of variables and is considerably more transparent about what these are at the start of each play-through. Before a level kicks off, you see, players are shown the Game Director hand of Corruption Cards, each of which influences how the proceeding action will unfold.

Some cards might, for instance, introduce environmental modifiers - disabling electricity to plunge all interiors into darkness - while others might dictate the enemies players will encounter, game-impacting events (such as a endless onslaught of zombie hordes), even optional objectives to complete along the way. On the latter front, the trailer shows a challenge known as Hasty Exit, tasking players with reaching the end of a stage within the allotted time.

Where things get even more interesting, however, is in the way players are able to assemble and deploy their own deck in response to the Game Director's hand - either choosing a pre-made deck to jump into the action as quickly as possible or taking time to decide which of their own cards, capable of imbuing a variety of buffs and bonuses, will be brought into play.

These might include cards that can boost individual stats such as stamina and health, Loot cards, cards that improve players' offensive capabilities (perhaps transforming a bash attack into a more powerful knife slash), even skill modifiers known as Talents, which might give secondary weapons unlimited ammo or replenish health whenever an enemy is killed by fire.

The idea is players can rise to the Game Director's sadistic whims by experimenting with different builds created using various card combinations - Turtle Rock's examples include decks built around medic, demolition, or melee specialisation - with more cards being unlocked using Supply Points earned through optional challenges and objectives.

Keen-eyed viewers will find a whole bunch of other card examples in the trailer, and if you're curious to know how Back 4 Blood is shaping up head of its PC, Xbox, and PlayStation release on 12th October, you can check out Martin Robinson's enthusiastic impressions of the game from earlier this year.