Halo 2 begins with a celestial siege. Thousands of alien lizard people, religious zealots with improbable jaws toting mean-looking laser swords inside their bulbous spaceships, crash into Earth to claim it as their own. Humanity’s only defense is Master Chief. The space marine is a walking tank whose face is a single head-sized Oakley lens. He’s gifted with a remarkable talent for blowing up whole squads of aliens. With the help of artificial intelligence embodied by what appears to be a nude, prophetic American Apparel model named Cortana and a turncoat alien called the Arbiter, ol’ Chief keeps humanity alive. Barely. It is patently ridiculous, an absurd action-figure collision as conceived by an 8-year-old drunk on Capri Sun and James Cameron movies. It remains, 15 years later, awesome. It became the best-selling entertainment release—not video game, but entertainment—of all time when it arrived on November 9, 2004.

This is the game that defined what mainstream video games are and how they play for the century to date. That Bungie, the video game studio that created the Halo series, began its work with an interstellar force crashing into the planet is deeply fitting. Halo 2 was the video game equivalent of the Chicxulub asteroid that may have caused the K-T extinction, wiping out the ecosystem that preceded it and making way for what followed. We can see the crater now when we look at everything from the way games control to the way YouTube stars build careers out of dicking around in Fortnite. Tom “Ogre2” Ryan, one of the very first American esports champions who made his first big money on the competitive scene that grew out of Halo 2, puts it more simply: “They created the prototype of how to do shit.”

What made Halo 2 so powerful on release wasn’t just how it made spacemen blowing up toothy aliens delightful, but how it made every aspect of blowing them up a collaboration. From the moment Halo 2’s trailer hit movie theaters—the first theatrical trailer for a game ever released—the game became something people did together. Halo 2 was the birth of the video game as we know it today: a mass shared experience.

Prior to the release of the original Halo in 2001, the video game industry was skeptical of Microsoft. It was an American software company with limited experience making things that were supposed to be fun, and it was entering a market dominated by entrenched Japanese companies like Nintendo and Sony that commanded an overwhelming share of people’s attention. Even Halo: Combat Evolved didn’t outwardly seem like a promising draft pick for Microsoft’s Xbox. While first-person shooters—games where you roam around and blast things from the point of view of a character—were popular in the wake of ’90s crossover phenoms like the famously violent Doom, Bungie’s game was supposed to be a profoundly different beast. Before Microsoft acquired the studio in 2000, with barely a year to go before the Xbox’s release, Halo was planned as a third-person action game with a heavy focus on strategy, exclusively available on Apple computers. When it was retooled as a first-person shooter, it barely made it out the door as a launch title for the game console’s release.

“The vision for the single-player game was realized in Halo, but the team also had ambitions to, in their words, revolutionize multiplayer with Halo,” recalled Max Hoberman, a veteran game designer who joined Bungie at the end of the ’90s and was the lead mind behind Halo 2’s multiplayer modes. “That wasn’t realized. Everyone was so busy just getting a single-player game out and getting it working on console that multiplayer basically got set aside. We just had to scramble and just throw something together, anything, together.”

What Bungie threw together was simple but ultimately effective. Halo: Combat Evolved was what sold the console, moving more than 5 million copies in the next three years and helping the Xbox sell a modest but impressive 1.5 million units in November and December 2001. People were drawn to the simple science-fiction toy aesthetic of Master Chief and the ability to play simple matches of games like capture the flag—one team of red Master Chief look-alikes trying to sneak into the home base of a blue team—with up to 16 people by linking up to four consoles together, not online but using ethernet LAN cables. Before the 2002 launch of online service Xbox Live, people would lug chunky black machines to each others’ houses, string them together with cords, and spend the night shouting at each other and laughing. “We had a big group of friends that lived on the street and that rode the school bus that played games,” recalled Ryan, who was 15 when Halo came out. “Something about it resonated with us and we just loved it so much.”

The reach of Halo was limited, though. Five million copies sold, even if tons of people were sitting in a dorm playing a single copy, wasn’t exactly reaching a blockbuster-sized crowd. Compare the numbers for the original Halo to those of the era’s dopey sci-fi standard bearer: Approximately 85 million people saw Star Wars: The Phantom Menace in theaters. Bungie and Microsoft weren’t reaching those heights, but their ambitions for Halo 2 were Star Wars–level in scope. To that end, Microsoft expanded the team of forward-thinking artists and storytellers beyond its internal staff and the crew at Bungie. Elan Lee, then an Xbox expat, was one of its secret weapons.

By 2003, Elan Lee had quit the Xbox team to help start a new company. Lee was barely in his 20s and had roots not just in the Xbox brand but Star Wars as well. He joined Lucasfilm to work on digital effects when he was just 18 years old before getting headhunted by Microsoft to work as the lead game designer for the Xbox console team. After getting the box out the door in 2001, he was cooked. “Everything we built there we had to invent from scratch. I really loved it,” Lee said. “I needed to resign because as soon as we launched the very first Xbox, Microsoft came right back around and said, ‘OK, get to work on the sequel.’ I was burned out.” He quit and cofounded 42 Entertainment, which specialized in alternative marketing and storytelling. Burned out on Xbox or not, Microsoft became his first client. 42 Entertainment kick-started the multifaceted communal experience that would eventually make Halo 2 so influential. Years before marketers started leveraging social media games—think scavenger hunts, contests, etc.—as a strategy to raise awareness, Halo 2 inspired a viral, shared multiplayer game before the actual video game was even done.

“‘A cultural event’—I remember that phrase set off little fireworks in my brain because no one had ever used such a grand statement when it came to telling a story before,” said Lee, recalling his conversation with former Xbox marketing director Chris Di Cesare, who brought 42 Entertainment into the Xbox fold. “‘We specifically want to tell a story that will be a cultural event.’ And that for me was world-changing. All I have to do is think up what the hell that is.”

“‘A cultural event’—I remember that phrase set off little fireworks in my brain because no one had ever used such a grand statement when it came to telling a story before.” — Elan Lee, 42 Entertainment cofounder

Lee, Susan Bonds, and the other founders of 42 Entertainment used the sci-fi setting of Halo and the appeal of the game’s basement get-togethers as inspiration for the unusual Halo 2 prequel called I Love Bees, a viral marketing campaign that used online platforms and pay phones to draw players in. Running from July 2004 to just before Halo 2’s release, Bees was one of the first alternate-reality games, similar to a story- and puzzle-based real-world scavenger hunt like The Dark Knight’s Why So Serious? or the myriad games associated with HBO’s Westworld. Alternate-reality games are, at their heart, mysteries that need to be solved through shared information. I Love Bees was one of the first. It told the story of that big alien invasion that opens Halo 2 in the last cultural window before MySpace and Facebook made social media ubiquitous. “I did what I always do: steal from people who are way smarter than I am,” joked Lee about I Love Bees’ genesis. “When I sat down to look at the script for Halo 2, it was a really beautiful story. Aliens invading, a huge epic narrative. And I realized this has already been done before. This is Orson Welles’s War of the Worlds.”

Luring people into a proverbial rabbit hole was the key to opening Halo 2 to that Star Wars–sized audience. The theatrical trailer for Halo 2 teased players with a very briefly glimpsed website domain: ILoveBees.co. The site was a honey pot, precisely crafted to come off as so alluringly bizarre that people would be drawn into the world of Halo 2 without realizing what was happening. It was conceived by a core crew of creators including Elan Lee and Susan Bonds, an engineer and the 42 Entertainment CEO who began her career designing Disney attractions like the Indiana Jones Adventure. Bonds said that I Love Bees was the answer to a simple question: “How do we increase the Halo effect?”

Anyone who visited the site was met with what looked like some apiculturist’s GeoCities fan page until it warped into a cryptic set of GPS coordinates and time stamps. When people started visiting those physical locations at the listed times, they found ringing pay phones. Players who answered the call had to correctly answer a question like “What’s my name?” that they’d have to learn by following updates on ILoveBees.co. Those that gave the right answer got to hear a first-person account of the invasion Master Chief was trying to push back, and they in turn would unlock that for all the people following along online at ILoveBees or on fan-curated pages like Bungie.org. The story was bananas. A network of artificial intelligences was sending warnings about the invasion back in time! Freedom fighters were barely keeping the aliens at bay! It was intoxicating. “The people who loved Halo already, now they have something new to talk about. [To everyone else now] they’re not those crazy people who sit at home with their Xbox and their controller,” Bonds said. “Halo 2 was about something that means something to every one of us: aliens showing up on planet Earth. I care about it because I care about me and I live on planet Earth and all of a sudden we got aliens showing up.”

“I realized this has already been done before. This is Orson Welles’s War of the Worlds.” — Lee

People got into it. “We had to call the police multiple times because our players got so into the act of answering these pay phones that they would get themselves in trouble,” said Lee, still baffled by the response years later. “We had reports of players trying to run across freeways. We had to intervene because these are people who are going to literally kill themselves to play this game.” One I Love Bees player in Florida went out into a hurricane to reach one of the pay phones. Someone plastered a poster for I Love Bees in the spin room of the third Kerry-Bush presidential debate and it was spotted by players when the room flashed on CNN. “We know that the group [answering phones] was somewhere between 15,000 and 20,000 people who really physically got out into the world and did something,” recalled Bonds. “And then we know how many unique IPs were helping put together the story because it had to be assembled online. We know that that was like 2.5 million people, maybe closer to 3 million people once all the press stories came up.” In 2019, we take this kind of stunt to get people involved in a game or movie as rote. (HBO’s Watchmen has its Peteypedia, etc.) In 2004, I Love Bees made Halo 2 feel omnipresent without also feeling predatory or cynical. By the time the prequel was wrapping up, Microsoft had already sold 1.5 million preorders for the game. The momentum was building. The way the game itself let people play together cemented its success.

“How do we top something that became a cultural phenomenon by accident?” This was the challenge facing Brian Jarrard, Halo community director at 343 Industries who joined Bungie back in 2003. He remembers the process of bringing Halo multiplayer to a larger audience. “How do we feed it, grow it, but make sure we don’t chop the legs out from under it?” he said. The answer was to bring the game online. At Bill Gates’s insistence, the Xbox offered broadband internet technology, even though only 9 percent of American households had broadband access in 2001. By the time Halo 2 released, that number had increased to more than 30 percent. Xbox Live, after more than a year in operation, had worked out most of its kinks and let Xbox owners get online to play with little of the hassle associated with doing so on home computers. “Xbox Live had been around for months before Halo 2 released, but there was nothing really paying it off,” said Frank O’Connor, current day director of the Halo franchise at 343 Industries. He also joined Bungie in 2003. “What Max Hoberman and the Bungie team built into Halo’s DNA with Xbox Live was recreating that couch experience online because that was where the joy was. Not, you know, ‘Here’s a bunch of server lists and you can join and hope you don’t get kicked out or join and get destroyed because you don’t have the skill.’”

Max Hoberman founded the game development studio Certain Affinity and joined Bungie as a user-interface designer in 1997. He went on to found the Bungie.net community and later designed Halo 2’s groundbreaking online multiplayer structure and game modes. Without Hoberman, there’s no playing Halo 2 on the internet. At least, not as people came to play it. When Bungie was forced to get the first Halo out the door under a breakneck deadline, it had to abandon more ambitious plans for its multiplayer modes. Hoberman said that the majority of Bungie wanted to completely give up the basic ways to play as a group that were packaged in the original Halo despite how strongly players responded to them. They instead wanted to make something revolutionary for expert players. After lobbying Bungie founders Jason Jones and Alex Seropian to evolve what had organically taken off at those LAN parties, Hoberman was put in charge of all multiplayer for Halo 2. The foundation was the Virtual Couch, a base for what his original design pitch describes as “a dynamic, friendly, intelligent online community.”

“We had to intervene because these are people who are going to literally kill themselves to play this game.” — Lee

“The idea was to make the experience of playing online as similar as possible to the experience of playing on a couch together in a LAN party,” Hoberman said. “You choose who you want to play with before you choose what you want to play, right? The way game matchmaking worked prior to Halo 2 is you really choose what you want to play first. That was the impetus for the party system, which was probably the biggest original invention in all of Halo 2 actually.”

Prior to Halo 2, playing a shooting game online on your PC was exactly like Hoberman describes: You would fire up the game, connect to the internet, and start looking at servers for a match with little to no guidance from the game itself. For most people, these were overwhelming technological and social barriers; you more or less had to learn two distinct languages to make the technology work and then penetrate the internal workings of every single game’s private world. Coupled with Xbox Live, though, Halo 2 placed you into a global community where you could reach out to your existing friend group in the same way you would on Instagram today. Search their username, there they are. Meet someone in a match, add them to your friend list. And all of it is anchored by the party system created by Hoberman. When you turned on Halo 2, you could pick which of your friends you wanted to play with regardless of what type of match you wanted to play or whether you wanted to play through the game’s story together. Today, in-game parties are standard in online games, an expected feature as common as the ability to pause.

So too is skill-based matchmaking. Rather than throw you into an unknowable pool of opponents, Halo 2 would look at how you played and pair you with people in generally the same geographic region and skill level. “Matchmaking didn’t exist. It wasn’t a thing,” Jarrard said. “We were terrified because for the fan community that was a huge sea change for them to wrap their head around, like we’re going to kind of be the DJ and sort of serve up games for you to play. Every single game on the planet nowadays has matchmaking now. You also have servers as an option, but matchmaking became the de facto just because it works. It’s super simple. It’s transparent.”

Favoring an open, welcoming approach to playing a game together was another Halo 2 innovation. “I’m not the best player,” Hoberman said. “I’m a good bellwether for going broader and making a game that’s far more accessible and doesn’t cater only to the top 20 percent of skilled players. I was swimming upstream in doing that because the vast majority of the people at Bungie were much more hardcore gamers.” It was Hoberman’s belief that the most important thing Halo 2 could do was make people that, well, sucked—beginners, parents, or casual gamers—feel like they could still hang even when they ultimately lost matches. The idea was that a Halo 2 match shouldn’t inevitably end with one veteran player shutting out a scrub 25 points to nothing. The scrub should, through luck or practice or stubbornness, walk away with some points for themselves. If the game was balanced only to the best, no one else would want to play. This was supposed to be a game for everybody.

Bungie got to watch people start playing it in real time the moment it hit shelves on November 9, 2004. The Bungie team rented out a party bus to take to a GameStop in Redmond, Washington, near the studio where they could hang out with fans waiting to pick up the game. They ordered pizza, joked about the game, and shared stories of Halo LAN parties. When midnight rolled around, though, everyone was gone. And the team watched the game come to life. “We’re high-fiving people and shaking hands and talking to people, but then when the store opened at midnight and people got their games, they just vanished,” O’Connor said. Back at Bungie’s studio, the team could look at a map of the planet, where every player connecting to the game’s servers appeared as a little light on the screen. Everyone was playing, even in places where Xbox Live wasn’t officially open for business. “Seeing that light in South Africa, in Cape Town, was stunning because to this day, when you look at online gameplay numbers, you’ll see the bulk of Africa is dark. The world shrunk by the arrival of it.”

The game remains a model for almost every game that’s followed, even in the PC community, whose rigid barriers Halo 2 worked so hard to remove. Apps like Discord go so far as to let you form parties before you decide what to play at all. Even Halo 2’s basic controls became the expected norm, cementing shooters around the controller rather than the mouse-and-keyboard-dominated ’90s. “You don’t have the one-to-one pixel precision of a mouse,” O’Connor said. “So how do we approximate that in a way that doesn’t feel like training wheels, doesn’t feel like you’re being guided, but works at that kind of speed with analog stick movement. And so you ended up with things like magnetism, stickiness, and so on. So you have these little assists that have always been designed to make you feel like that’s a natural extension of your ability. And that’s still true in almost every FPS game.”

In its first year, Halo 2 sold more than 7 million copies, 2.3 million of which it did in just the first day, far outpacing its predecessor’s lifetime sales on Microsoft’s debut machine. While those aren’t quite Star Wars numbers, Halo 2 made $125 million in a single day, more than even the highest-grossing opening weekend box office of any movie up to that point. People played 710 million hours of the game by 2006. “We suddenly began to look at one true global community,” said Brian Jarrard, “which was pretty amazing, but also kind of terrifying to be honest.”

When Tom Ryan and his brother Dan started playing Halo and exploring the tiny tournament scene that existed in the United States before 2004, they were playing for fun, or a little modest glory. “Our first tournament was at Ohio University about two hours away,” Ryan said. “I think the prize was like 200 bucks in gift cards or something. It might’ve even been like 50 bucks.” By the time he was known as Ogre2, dominating Halo 2 tournaments in the mid-’00s, he was creating the model for modern esports celebrity. Even though Halo 2’s monumental success grew out of a broad, accessible approach to bringing goofy sci-fi to the public—through pay phones, through considerate design, through sharp iconography—it also altered the landscape of professional gaming. Prior to the fall of 2004, the nascent competitive scene in the U.S. was restricted to college campuses and basements. Halo 2 gave birth to the big spectator incarnation of American esports that exists today.

“We suddenly began to look at one true global community, which was pretty amazing, but also kind of terrifying to be honest.” — Brian Jarrard, Halo community director at 343 Studios

“Esports in general wasn’t really a thing in North America. Counter-Strike was big in Europe. StarCraft was going on over in Korea,” Ryan said. “That’s when the scene in the U.S. blew up with Halo 2. … We were really excited. We knew that we’d be able to play online and we could really like take it to the next level. Holy crap, this is cool. We can travel around all year and make some decent money.” Ryan recently took over as general manager of the Call of Duty League Florida franchise, which is part of one of the dozens of global esports leagues currently operating. The Call of Duty League tournaments spawned out of Major League Gaming in 2016. MLG itself was founded in 2002, but its first televised big-money competition? That was 2006’s Boost Mobile MLG Pro Circuit, a broadcast of Halo 2 Pro Series. “People always ask us: Are you jealous or do you wish you were born like five or 10 years later because you would’ve made millions in prize money instead of a couple of hundred thousand over 10 years?” Ryan said. “The silver lining is we feel like we had a lot more fun. It was a more intimate scene.”

Max Hoberman also sees an object lesson in Halo 2 for any game maker trying desperately to gain a foothold in esports. The key is: Don’t force it. “You don’t actually design for esports. Esports players will go where the fans are. They’ll go where the players are,” he explained. “[Build] for the pro player only, you’re actually building for a different audience, not for a mass market audience.”

Halo 2’s influence and success can’t just be measured in terms of sales and how it broadened the actual direct gaming culture, though. Halo 2’s impact also presaged how people would start taking the internal worlds of video games and start making entirely new work with them. Streamer and YouTube culture have genetic links to the game. “They took things that worked on PC and made them much more affordable, made them much more mass market, and here was a game that you could play and you could buy a console and you didn’t have to worry about like how to set up a network,” recalled Burnie Burns. He is the cofounder of media company Rooster Teeth and its signature show Red vs. Blue, an animated comedy made directly in Halo and its sequels by recording people playing it in comedic ways and then recording dialogue over the footage. Burns was a journalist and video producer when the first installment of the franchise was released in 2001. By the time Halo 2 came out, he’d founded Rooster Teeth and was working on his show full time.

Red vs. Blue is still in production. Its 17th season wrapped up in May 2019. Looking back, Burns credits Red vs. Blue’s audience explosion to the fact that the show came out exactly 18 months after the release of Halo and 18 months before the release of Halo 2; he was riding the wave of that growing audience. When Halo 2 finally came out, he discovered that Bungie was starting to recognize that people were using the game together even beyond store and competition. Red vs. Blue was built out of Halo. The characters, the settings, the Looney Tunes–style sight gags of a character blowing up and falling on their face—all of it was “shot” in the game itself. But it wasn’t necessarily a Halo show. It had its own characters, its own mythology, and its own rhythm that was distinct from the game itself. Burns’s creation took Bungie’s game and made something entirely new with it. Halo 2, in turn, reflected an understanding among its creators that this was one more way people would start playing with their work, and they were giving tools to the audience to make their own fun.

“You could see the beginnings of it in Halo 2 because they started adding features that had no purpose for playing the game whatsoever, like dropping the weapon,” Burns said. Pressing down on the D-pad, that little cross that’s come standard on almost every controller since the mid-1980s, would let your character in Halo 2 lower their weapon to their side. It let the character model look just a little bit more relaxed, a little more at ease. The pose doesn’t benefit you in any way in the game; you can’t lull people you’re playing with into a false sense of security or something. The pose is there purely for storytelling potential, and it was just one of many little changes that made Rooster Teeth’s work richer, more detailed, and easier to craft. “Those little tools to help you shoot things were revolutionary and I think those are what led to theater modes,” Burns said. “Theater Mode is such an important part of the Halo franchise. That it had this incredibly robust replay engine where you can replay your games. The ability to replay didn’t exist and Halo had it seven to 10 years before anybody else was doing it.”

Halo 2’s roots run both wide and deep: It planted the seeds for professional esports athletes and content creators, formalized infrastructure for playing games online, and fueled social games in the wild that froth people up to the point that they’re willing to answer a pay phone in a tropical storm. But it is also, occasionally, ugly. There was no shortage of pointless bickering and hateful trolling on the internet before 2004, but the roots of the omnipresent bellyaching that is synonymous with the gaming industry also sprang from Halo 2’s soil. Some people, naturally, didn’t like the game. What was different was how it manifested. Today it’s not uncommon for game developers to get death threats after putting a game out in the wild. Bungie saw someone register the domain Halo2Sucks.com within a few weeks of release. (It’s still up, with a fresh copyright no less.)

“It was my first experience of negative community,” O’Connor said. “People complain about stuff. That wasn’t unusual, but it was my first glimpse at organized and miserable bastards whose passion is for complaining about a thing.” What the team saw was that the more the community expanded online, and the more they felt they had direct access to the creators of the game themselves, the angrier that community seemed to become. It wasn’t necessarily that everyone was dissatisfied—far from it. It was that the loudest voices tended to be the most negative ones, a familiar ratio for anyone who’s spent any time on Twitter this decade.

“It’s a poop-in-the-swimming-pool proportion,” O’Connor said, utilizing the elegant language of Caddyshack to embody the impact of internet haters. “Somebody leaves a normal-sized dump at the far corner of an Olympic-sized swimming pool. Well, it doesn’t matter that that’s a vanishing percentage of the volume of the pool. So you end up realizing that these loud, negative voices aren’t representative.”

In the case of Halo 2, the negativity around the game—e.g., accusations that the story was truncated—fueled Bungie’s development of Halo 3, which followed on the Xbox 360 three years later. Halo 3 raked in $170 million in its first 24 hours alone, going on to sell 14.5 million copies and breaking the sales record set by its predecessor. The series moved on, Bungie left Microsoft to establish its successful Destiny franchise, and O’Connor and other veterans established 343 Industries to keep the series running. Halo 2’s records have all been eclipsed at this point even though the game still, even now, has a community of players. (“It’s definitely still there,” said Jarrard of the Halo 2 scene. “It’s smaller of course than it used to be. Some of these communities have just never moved on.”) But its matchmaking, its approach to bringing people in, its controls, the standards for pro competition it established, and its philosophy on communal world building as reflected in things like Red vs. Blue and I Love Bees all still represent best practices for everyone making things for other people to play. When you see some seventh grader posting a TikTok recapping their Fortnite match from the night before, the moment’s rooted in Bungie’s stab at making a cultural event. Why do all of Halo 2’s parts still work in modern engines?

“Because they work, right?” Hoberman said. “If they don’t work, someone’s going to invent a better mousetrap. But the reality is a lot of systems I developed, they still hold up today because they work. Why are we still driving cars that work off of exploding gasoline in a confined space?”

It seems impossible in 2019 for a game to completely upend its medium like Halo 2 did back in 2004. People are too ensconced in an avalanche of media and of choices for something like it to feel so huge and for its affect to be so far-reaching. “A cultural event today is defined by a much smaller group of people,” Elan Lee replied when asked if something like Halo 2 could happen again. How do you make something for everyone when everyone is siloed off into little pockets of their own curated entertainment? “I think that that’s going to be almost impossible for original works,” Burns said. “People who bankroll those are going to rely more heavily on adaptive projects. It’s just the way the world works. So we’re not going to have the Halo 2, we’re not going to have an Empire Strikes Back again for a while.”

When it happens, though, when we finally see the next Halo 2, the thing that lands and changes the very landscape it touches, it will succeed for the exact same reason Halo 2 did: It will be something shared.

Anthony John Agnello is a writer and editor living in Ithaca, New York, who covers video games, human beings, and climate change. His work has appeared in The A.V. Club, Engadget, and other publications.