Left 4 Dead 2 received one of its last updates late last year, as part of a community-led expansion of which Valve gave its blessing. Beyond that, it had been almost eight years since the last update for Valve's version of the co-op zombie survival game. Before that was Turtle Rock Studios' inaugural effort in the original Left 4 Dead, a formative game for co-op survival titles that inspired many co-op titles beyond it. Now, the studio has returned with Back 4 Blood in its first largely public test, as the upcoming open beta starts this weekend.

Turtle Rock Studios' latest co-op survival game finds itself in an interesting place: a dedicated and largely traditional Left 4 Dead-esque gameplay experience, built with modern features in mind to better accommodate replayability and quality of life. Back 4 Blood is being designed with both old Left 4 Dead veterans, as well as new players unfamiliar with Left 4 Dead, in mind. As executive producer Lianne Papp puts it, she hopes that for any cautiously optimistic Left 4 Dead fans that Back 4 Blood "fits, and it works, and it feels good." For the most part, that's a true assessment of Back 4 Blood as the game moves into its first public beta.

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Much like the foundational Left 4 Dead games that it's based on, Back 4 Blood comes with two main threads of gameplay: The PvE campaign missions similar to the alpha test late last year, and the "Swarm" PvP mode that's new to this public beta test. Rather than the versus modes from Left 4 Dead taking place in existing campaign missions, Swarm is a more open-ended, standoff-style mode. It's just Cleaners vs. Ridden in sandbox maps full of loot and vantage points that encourage coordination.

Rather than running the gauntlet of a full campaign through Back 4 Blood's PvE-centric routes, Swarm mode keeps things short, sweet, and thrilling. Teams of four compete to survive the longest as Cleaners (survivors), vs. the Ridden (infected), switching sides each round until a winner is determined within three rounds. A surrounding ring of "insects" swarms the cleaners and condenses the map to make Ridden attacks progressively more overwhelming until the round concludes.

At a base level, Swarm certainly accomplishes its goal of being a more streamlined and fast-paced version of Back 4 Blood's zombie co-op action. It's difficult to comment on the overall competitive balance of it all based on a short preview period, but there is a degree of complexity in choosing which Ridden to attack the Cleaners with. "Tallboy" Ridden are incredibly strong tank-style enemies that can obliterate Cleaner health in close range, while "Stinger" class Ridden can assault survivors at range to chip away at their health.

Cleaners, on the other hand, have to make the best with their time by scavenging for optimal loot in the short span of time they're given before a round starts. From there, keeping Ridden back is largely based on sightlines and holding flanks, because the infected can only spawn outside of a Cleaner's cone of sight. Keeping a tight circle between teammates is critical for long-term success in Swarm; the map is only going to get smaller, and there's only so much ammo and time before survivors are defeated. It's an interesting way to impede what would otherwise be an oppressively one-sided challenge for Back 4 Blood PvP.

Beta players will certainly come to understand what the best strategies to survive the longest are in Back 4 Blood's Swarm PvP, but for now, the mode is promising. It's a deceivingly simple, but still very challenging iteration on the previously established Left 4 Dead versus design that should act as a good palate cleanser between rounds of Back 4 Blood's longer and more traditional campaign/PvE mode.

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One aspect of gameplay design that's unique to Back 4 Blood is the degree of flexibility and customization allotted to each mode. Left 4 Dead essentially presented players with its refined gameplay experience as is, but Turtle Rock Studios' latest zombie co-op experience attempts to up the ante in one unique way: Back 4 Blood's unique deck and card system. This card system most tangibly affects the PvE experience, but there are separate cards and decks between PvE and PvP modes.

Whether it's something as simple as +10 health or higher accuracy, or something as pivotal as one free revive or breakout from a Ridden grab, Back 4 Blood's card system is an interesting way to give players a leg up. Especially in higher difficulties, where the zombie survival challenge is much more relentless, optimal cards and decks can be essential to survival. Each checkpoint and safe house in PvE allows players to choose one card to augment their abilities (and potentially their team) in the next chapter.

Cards are a double-edged sword as well, as "Corruption Cards" also trigger in subsequent chapters as well, augmenting the Ridden's ability to attack players. Corruption cards could either trigger in-game events or obstacles that could cause some serious damage to Cleaners if they're not careful.

This is arguably the most interesting way that Back 4 Blood encourages replayability. Corruption card changes make each campaign scenario distinct and different, even if it's the same map with a new challenge. There were only a few Corruption card changes experienced in the preview, but they did tangibly change the experience of navigating each level of the campaign, even after a team wipe and subsequent retry.

Overall, Turtle Rock Studios does have something special on its hands with Back 4 Blood. Iterating on the Left 4 Dead formula it once established in meaningful ways, the efforts Back 4 Blood makes to encourage replayability are enticing just based on this short preview. The Swarm mode made PvP genuinely interesting, even if it is comparatively bite-sized next to the longer PvE campaigns. Assuming the balance experienced in the preview extends to this weekend's beta, Back 4 Blood is shaping up to be a thoughtful and modern return to the zombie co-op multiplayer experience that Left 4 Dead fans adore.

Back 4 Blood releases on October 12, 2021, for PC, PS4, PS5, Xbox One, and Xbox Series X/S.

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