10 Years of Left 4 Dead: Hunters and Boomers and Smokers, Oh My!

The mid-2000s had a lot of great zombie games, but none pushed the envelope like Left 4 Dead. Not only did it influence the future of asymmetrical multiplayer, but it simultaneously innovated in the realms of AI and cooperative game design. It’s hard to believe 10 years have passed since our first encounter with the Green Flu.

Left 4 Dead tells the story of the four unluckiest people in the world: a Vietnam veteran, an office drone, a college student, and a biker who hates everything. Their goal is to cross a dangerous landscape full of infected, unintentionally making as much noise as possible, until they reach an evacuation vehicle, which will invariably break down and leave them stranded at the start of the next adventure.

The original release shipped with four campaigns, each played out in five chapters. The goal of each chapter is to run through hordes of zombies to reach the nearest safe room, where you can stock up on first aid kits and ammo. Along the way, hectic crescendo moments will challenge you to think strategically and defensively as the only way to proceed is to create a tremendously loud sound that attracts every zombie in the tri-state area.

The zombie’s ferocity is part of Left 4 Dead’s charm. The common infected aren’t your classic, shambling Romero zombies. If you’re lucky, you’ll only be fending off sickly marathon runners. The standard infected will outrun you, and when they catch you, they’ll cause damage, and they decrease your movement speed. These choices make hordes imposing, even if they're easily dispatched with a single shotgun blast.

Then there’s the special infected. There’s the grab-and-pull Smoker, the pounce-and-rip Hunter, and the Boomer, who is basically Monty Python’s Mr. Creosote. Oh, and don’t forget about the Tank, a boss monster who's basically an enormous ball of muscle and anger. His role is to roll up into your defenses and make survivors cry on higher difficulties. When you hear the tank’s theme song, you know it’s about to get real.

Giving each special infected a special audio cue on spawn was a clever idea. It lets the survivors know there’s a threat lurking somewhere, even if they can’t see it.  When multiple special infected are on the map, those audio cues can throw off the survivors and trick them into an ambush. You might hear the Smoker theme and decide to hide in close quarters, only for a hiding Boomer to jump out and blind you with his infected-attracting bile, allowing the smoker to pull someone away.

There’s also the Witch, a sobbing special infected who often spawns in the most inconvenient place possible. Irritating the Witch will cause her to freak out and incapacitate or kill the person who startled her. While she sounds imposing, she’s ultimately a non-issue, even on expert difficulty. A well-placed blast from the automatic shotgun will take the Witch out before she has a chance to be startled.

I used to scare my teammates when I’d charge an expert difficult Witch and put her in the dirt before she turned violent. While the Witch has great synergy with the other special infected, especially the Smoker, she’s a pushover on her own.

More than anything, Left 4 Dead’s special infected recontextualized cooperative survival games. The special infected are designed around cooperative play; once they’re in action, you cannot take them alone. The Hunter, Smoker, and Witch are designed around completely incapacitating survivors, leaving them helpless, while the Boomer and Tank undermine defenses and distract would-be rescuers.

Allowing special infect to completely incapacitate players makes desperate survival moments especially tense. When you’re down to two survivors, a well-timed attack from a Smoker and Hunter can end the game outright.

Special infected force survivors to cooperate and share. A survivor with 80 health wouldn’t think twice about giving their only first aid kit to an ally. That's the key: Keeping the group alive is the best way for players to ensure their own survival. It’s a rare case of developers forcing selflessness as a foundational element of gameplay and players accepting it.

The cooperative aspect is further enhanced by a few small design choices. The most important decision was to make fellow survivors visible through walls. This is a small feature, but it does a lot of work. First, it means nobody is left for dead before triggering a crescendo event. Second, it informs you of your defenses at a glance. This is especially important for finales, where you'll immediately know whether someone is watching the flank. Third, it helps players find downed survivors, making it easier to help someone who was pulled into the dark by a smoker. Seeing other players' health bars and always knowing where they encourage players to stick together and give each other support.

Survivors aren’t the only ones who need to cooperate. In Versus mode, two teams of four play as survivors and special infected. Left 4 Dead's competitive mode is unique because one team is forced to rely upon randomly generated AI to win. At the time, that was a huge step for asymmetrical multiplayer.

The infected team primarily uses three class types: Smoker, Hunter, and Boomer. Additionally, one lucky player gets to play Tank during crescendo moments. Because each infected has a specialized role, they won’t be able to incapacitate survivors outright. While infected players rely on the common infected to chip away at survivors and slow them down, the Boomer is based around summoning hordes of AI fodder. Infected players must strike at the right moment to cause maximum chaos, usually during a horde encounter.

All this AI randomness is thanks to Left 4 Dead’s most impressive innovation, the Director. The Director is a backdoor entity constantly keeping tabs on how you’re doing. It monitors the perceived intensity of an encounter by calculating the damage players take concerning the number of infected they’re killing. If you’re dominating, you’ll get more horde encounters and pain pills. If you’re struggling, the director sends you fewer infected and more first aid kits.

The Director uses intensity to cycle through three modes: Build Up, Peak, and Relax. Build Up is “normal;” Common infected pepper the map, and special infected wait in the shadows. In this mode, common infected aren’t actively looking for you. They’re basically scenery, stumbling around until you give them the old spinal tap. Make a loud noise, and the horde will descend on you in a matter of seconds.

The Peak cycle occurs when you’ve alerted the horde. The director stops spawning additional zombies so you can roll straight into Relax mode. This final mode gives survivors less than a minute to heal, reload, and move to the next area undisturbed. Then the cycle starts again.

Like the special infected, each of the Directors modes has its own sound cue. There’s even a special cue for a horde appearing out of nowhere. If you're aware of intensity, modes, and Tank spawn points, you can almost predict the Director’s moves. When you kill the last infected, it’s time to heal and move as fast as possible.

The Director's presence in Versus mode is interesting because the game devolves into controlled chaos. The Director will keep doing its thing, but infected players can use the sound cues and intensity to maximize their attacks. Likewise, survivors who know only 30 common infected can spawn at a time can count the number of kills needed to hit the next Relax cycle.

While predicting the Director is some serious metagaming, it’s interesting to peel back the curtain and see the man behind the curtain. Of course, predicting the horde isn’t easy, and the Director may throw you for a loop now and then.

To this day, Left 4 Dead remains an interesting exercise in cooperative survival games. It did a lot for the development of asymmetrical gameplay, cooperative game design, and AI technology. While Left 4 Dead 2 improved on almost every aspect (going so far as to release a DLC replica of the first game with new mechanics), the first game holds a special place as another memorable entry from Valve.

I only wish there was a Left 4 Dead 3.