When Games Played You, Too
Exploring the micro-trend where horror games responded to player behavior, featuring the iconic Left 4 Dead series.
Content Warning: this article is very design-focused, so there’s very little in terms of sensitive content addressed in this one. However, there are some images of zombie designs, so if you’re not a big zombie-enjoyer, this one might not be for you.
Overview (and Disclaimer)
Let's be honest. There's been a lot of discussion about AI in the past year. And all of it is garbage. Seriously.
"AI" as it's been discussed in the mainstream media is specifically referring to generative AI. That is: tools that are fed "scraped" (read: stolen) data of everything from art, to photography, to text, with the intention that the program would be able to replicate or otherwise "spit back" generated material. Shills for this technology heralded it as some kind of innovation that could potentially put the entire art and games sector out of work (except it can't), will save the world (except it won't), and even spur on scientific discoveries in some kind of technologically-driven renaissance (except it literally cannot conduct its own research you guys it requires existing stuff to be fed into it, it's not capable of its own thoughts). Anyway.
Generative AI is a funhouse mirror. It spits back ill-formed versions of the authentic. It's not interested in genuine composition or artistic intent. The only people who are excited about this possibility are the execs who can use it to dazzle shareholders and dilettantes unwilling to learn to draw or write, themselves. But what we're going to cover in this article is, in itself, a form of artificial intelligence - however the phrase "AI" has been overtaken by the aforementioned shills who don't understand why humans make art in the first place.
In truth, artificial intelligence is just a category of machine learning, which has been utilized in many aspects of the arts and sciences for decades. Video games use AI all the time! Think about enemies and their behaviors: how they move, how they attack - all of that is an AI package. If you're playing one of those "map coloring simulator" strategy games, and you notice that two countries nearby on the map are having a war - that's AI at work. Procedurally generated narrative, or levels, or any of that... that's AI. But it's not generative AI. That's the difference.
So for the purposes of this article, I want to be very clear what I mean when I say “AI,” because I am in no way referring to the generative stuff. But discussing legitimate applications of this already-existing tech feels weird now. Because the AI bros took that from us. Ok? Ok.
Machine Learning In Horror Games
The horror game scene in the 2020s is experiencing a golden age. We have absolutely no shortage of incredible games to play: from indie to AAA and everywhere in-between. Like many genres, horror experiences a natural ebb and flow in its media production. And like most media industries post-2008-financial-crisis (the way this keeps coming up in my articles is weird and makes me kinda angry ngl), there was a natural slowdown in production (even though video games have previously been considered "recession-proof").
While all genres interact with whatever the general public is facing at the time of creation, this goes doubly for horror. Since the genre is characterized by confronting that which we find uncomfortable, shameful, or frightening, the genre also develops natural ebbs and flows in terms of its content. And in horror games, this is also influenced by the technological advances of the era. When new technology allows for a new mechanic to be supported, everyone naturally wonders: who is going to do it first? Who is going to do it best? And this often requires a certain degree of experimentation.
So post-2008-financial-crisis, horror games knew that they would have to do something pretty bold in order to receive funding and make it onto the shelves (back when there were literal shelves).
And with new technology that was coming online, there was a trend surrounding a new convention: what if a game was able to learn your playstyle or fears and was able to respond in real time? This mini-era in the 2010s was full of experimental titles that attempted learning your behavior as a player, what you were afraid of, and modulate itself accordingly in order to meet those needs. And you might say: that sounds like a tall order. And it was! But that's the thing about video games. They so frequently like to push things forward.
Titles of this era which boasted “the game plays you” technology:
Until Dawn (2015, 2024 remake) - I want to do an entire dedicated analysis on this one, so watch this space. When will this happen? Who knows.
Silent Hill: Shattered Memories (2009) - this lesser-known entry in the iconic franchise used a “psychological profiling” system to determine what horrors await the player.
Anna: Extended Edition (2013) - naturally I played this one at release because it’s my namesake, but I was never entirely convinced the game was that responsive. It’s about a witch named Anna though, so, tbh, same.
Nevermind (2015) - this title claimed to utilize biofeedback to learn and exploit your fears. Considering the available tech during this era, I’m curious how successful it was. If you’ve played this one, sound off your thoughts below - I wanna know!
And you might be like “Anna… you missed one. Or, two, rather. The two which arguably did it best. To which I say: what do you think the article’s about, silly?
I was originally going to do a snapshot of a couple of the games listed above, but I fell so deep down a rabbit hole researching one specific aspect of this franchise that I decided to dedicate the entire article to it. That’s how much I love your games, Valve.
The Left 4 Dead Series and its “Director”
The first time I really learned about machine learning and artificial intelligence in a horror setting was in Valve Software's Left 4 Dead franchise, which is comprised of two installments: Left 4 Dead (2008), and Left 4 Dead 2 (2009).
The backbone of this squad-based zombie-shooter was a system known as The AI Director, often just referred to as "The Director" or "AID" for short. The Director was present in both installments, however it had a beefier and more nuanced set of supported features in the sequel due to continued iteration and upkeep, as it was clear to Valve that they had a smash hit on their hands.
The AI Director allows the game to constantly modulate itself to squads of more (or less) experienced players. Variety of weapons, enemies, and consumables kept the game feeling fresh on replay, and it’s my opinion that it’s one of the reasons this franchise has aged so well. Playing Left 4 Dead 2 in 2024 is just as satisfying as it was at launch. And once I started looking into it, I learned there were things the Director was doing that even I, a dedicated Ellis-main and Left 4 Dead veteran, was unaware of. So let’s take a look!
Zombies and Enemy Spawning
Perhaps the most commonly-known feature of the AI Director is its ability to determine the number and variety of zombies that the squad will encounter. Doing well? Not taking so much damage? More zombies - and zombies in trickier places (such as close-quarters)! Struggling a bit? It’ll toss you fewer zombies and mostly in less challenging places (such as sticking to wide-open portions of the map)! The constant variety of location and variation of enemy spawning makes the relatively small number of playable maps (at least compared to modern titles) feel fresh round after round.
However, the Left 4 Dead franchise pioneered the introduction of specialized zombie varieties that go beyond your typical shuffling corpses. Known as the “Special Infected,” this class each has a unique set of behaviors: such as pouncing from above on one member of the group, or spitting pools of noxious acid.
These special infected often target individual players who have wandered off from the group. This also shapes gameplay, as sticking together and working collaboratively become the best protection from these weird little guys. But, for example, if your squad is very good at sticking together and taking down the undead, the Director may throw more Chargers, Jockeys, and Smokers at you - specials whose attack behaviors attempt to isolate one member of the group, allowing them to be “picked off.”
Sometimes, when the Director is feeling particularly sadistic toward an experienced squad, it may place a Witch (a deadly special infected that will only attack when you get close), in the middle of a narrow hallway, making her unavoidable. Or alternatively, another common technique, toss a Boomer at you right around a corner, making it so their explosive hoard-calling abilities are unpreventable. But all’s fair in love and zombies.
Health, Weapons, and Consumables
But it’s worth noting that The Director is not an entirely adversarial entity. It’s “listening” to the amount of damage done, but also the amount of damage taken. While most consumables and weapons are auto-populated from a dataset on load, if players are consistently at low health-levels, the Director may choose to provide more pain pills in the first-aid boxes throughout the map.
First aid items vary in usefulness and application: from providing a temporary, non-substantial boost to bringing a deceased/fallen squad member back from the dead. But increased frequency and swapping more substantial items can help players make it to the next Safe House, where there’s usually more substantial consumables available.
Level Traversal
This is what surprised me the most. Only available in Left 4 Dead 2, The Director can literally choose to make changes to the map in accordance with how well the players are progressing throughout the chapter. These changes vary in how much they will differentiate the player experience: from switching the location of spawn points to entirely altering the player’s path.
For example, in The Cemetery portion of The Parish, the graves/mausoleums themselves are dynamic, meaning that the AI Director could force the players to take a longer, less direct route if they need a bit more of a challenge. This may also be coupled with spawning more zombies or special infected to really up the ante.
Or, there’s my personal favorite map, Dark Carnival, where the game may spawn a fence along the main path, providing an extra layer of protection between zombie and player should the player needs a little assistance.
And in most people’s least favorite map, Hard Rain, the torrential downpours which completely drown out the sounds of your fellow squamates and obstruct your vision are controlled by the AI Director. May it have mercy on our rain-drenched souls.
Gameplay Flow and States
The gameplay flow of the franchise is unmatched, and that also comes down to the “state system” managed by the AI Director. This system is predicated on the players’ “Intensity level” which is a variable calculated by how frequently they are taking (and doling out) damage to/from enemies at close-range. The Director is keeping close tabs on the individual and collective Intensity levels in order to determine when to throw another wave of the undead your way.
There are three states in total:
Build Up: from the moment the players spawn into the map, Build Up mode begins. This is the “onramp” for Intensity, and is the closest to what you can probably determine “normal” spawning patterns for both regular and special infected. The goal is to slowly raise Intensity level until you hit…
Peak: when all players are at Maximum Intensity - the electronic-sounding attack music is blaring, your screen is covered with blood, and you’re genuinely not sure if you’re going to make it out of this one alive… the Director actually stops spawning new infected, allowing the player to clear out the rest of the zombies and feel a great sense of satisfaction to boot.
Relax: after Peak comes the Relax phase, wherein no new enemies will spawn (except for some random one-off zombies called Wanderers in L4D2, who don’t really pose that much of a threat). This unassuming state in the triad is actually critical: it allows players to take a moment to breathe, maybe use some health items, and return back to a lower level of Intensity. It’s this part of the process that actually allows for there to be a real feel of “flow” in the game, rather than the player just getting overstimulated by nonstop flailing limbs. I gave an entire talk about “quiet moments” at PAX 2020, and am considering converting it into an article here. These “cool down” periods are actually the most important, IMO.
But there’s actually one more phase that isn’t commonly covered in various talks and YouTube videos about the architecture of this franchise’s Director: it can be shut off.
At the end of each campaign is a “finale” phase (such as The Boathouse, seen above). These chapters have their own specific patterns of waves and scripted events independent of the state system mentioned above. As such, the AI Director is switched off to save on performance (finales are already pretty resource-heavy, having the AI Director running in the background could cause framerates to dip), and otherwise to prevent bugs and friction. The ability to switch it off is as genius a feature as anything.
Conclusion
Truly, the enduring legacy of this series is how it often makes me get a lil mad at how slick it’s designed. Since the era of the Left 4 Deads, many other games have utilized complex AI Director systems to make enemies more intelligent or have more sophisticated behaviors in service of delivering a good scare. See: Alien Isolation, or the Resident Evil remakes.
But when it comes to a game that really plays you as much as you play it, I haven’t found a single one that can touch this franchise. And I truly think that’s one of the reasons it has remained such a titan in the multiplayer world.
…In fact, I might just have to reinstall it and jump back in.
Thanks so much for reading. The Left 4 Dead series was already a few years old by the time I got to it, but it became such an integral part of my high school experience - and later the pandemic when my friends and I got into it again. It’s like the comfort food of zombie media (don’t tell Resident Evil I said that).
As mentioned above: have you played any other games with cool AI Direction? Let me know! And as always, I’ll catch you in the next one!
The game that did me was Outlast I think. I think I lasted 30 minutes and was like nope. No thank you and goodbye.