Early last summer, at 3 a.m. in the South Bronx, an agent named D Skully was getting frustrated. Staring into a black-and-green grid on his smartphone, he attempted to secure a target for his team — but every time he thought he'd nabbed it, it'd get stripped away. He looked around; nobody else was out.

Suddenly, D Skully spotted a girl's face illuminated by the light of her phone screen in a small car parked down the street. As she remembers it, he went and knocked on her window to confront her, and as soon as she was caught, the car peeled off.

The two of them were playing Ingress, an alternate reality game (or ARG) run by a Google startup called Niantic Labs. Ingress is like a giant game of Risk or Capture the Flag, only the game board is the entire world. The goal is to capture as many "portals," or in-game waypoints and locations, and hold them for your team for as long as possible.

Except unlike other mobile games, Ingress players — known as agents — have to run around city streets, parks, alleys and backcountry destinations in order to win. The game is played by millions of people, and if you're in a major metropolitan area, chances are that Ingress players are all around you.

To play Ingress, players have to move around their local neighborhoods and find "portals" to capture them for their team. Ingress/YouTube

So how do you play? Ingress is played entirely through a free app for both Android and iPhone. Players are divided into two factions — the Enlightenment (the green team) and the Resistance (the blue team) — and they run around the city, collecting keys, weapons and upgrades, and capturing portals for their faction.

Each portal is tied to a real-life landmark: a famous sculpture, popular storefront, train station, whatever. But players are tracked via GPS, and to capture a portal, a player needs to be physically near that landmark. So if you want to capture the local bus stop across town for your team, you've got to put sneakers to pavement.

Control for cities and portals is measured in daily cycles worldwide, and each captured portal contributes to your team's global score. Triangulating and linking portals for your team lets you set up control fields, which rack up more points for your faction.

Linking portals together creates a "control field." Ingress/Youtube

Ingress is played around the world, and John Hanke, the head of Niantic Labs, told Mic that Ingress is growing not just in the U.S. but in Europe, East Asia, India and the Middle East — anywhere with reliable public transportation and large groups of people who congregate outside.

The game has been downloaded more than 11 million times in its two-year history. Hanke says there are currently more than 1 million daily active players. Take over a portal in a city as densely populated as New York, and you can bet that by the end of the day you'll get a push notification telling you it's under attack.

For example, this is what midtown Manhattan looks like at any given time. By the time you're reading this, many of the portals, if not all of them, will have changed hands.

Mic/Ingress

Niantic Labs is a small company, and Ingress is supported by a staff of fewer than 100 employees. They keep the game running, communicate with local communities, build the in-game storyline and release regular battle-report videos. To run the game, though, Niantic looks to the active Ingress community to submit suggestions, coordinate teams and even create the portals.

"There's no way to have a team large enough to craft a game across the world, so we have people identify the important places in their world," Hanke said. "Nobody is going to know the neighborhood as well as the people who live there."

The Ingress community is thriving. A New York gamer named Daniel, whose "agent name" is Landieaccem, told Mic he started playing when Ingress was still in beta testing. There were almost no other players holding it down in his home neighborhood of East Harlem, so he immediately started submitting portals and aggressively defending his territory.

A beginner, he'd claimed an enormous swath of land from 106th Street to 124th Street. Eventually, someone took notice.

"A couple of agents contacted me, and they invited me for a couple of drinks," Daniel said. "There was this moment, like, 'How far down does this rabbit hole actually go?'"

That's when David was pulled into the Ingress scene in the New York area. For more than two years, the local factions have run around the city largely unnoticed by both bystanders and press. Meanwhile, David and hundreds of others have coordinated meet-ups, gaming events and coordinated assaults against the Resistance forces in New York, where there's a friendly rivalry.

"There was this moment, like, 'How far down does this rabbit hole actually go?'"

Ingress players think of themselves not as a gaming group but a community that's in touch with one another every day. The Ingress players Mic spoke to go out for drinks, visit one another in their homes, attend one another's birthdays and college graduations — they build lasting relationships. Outside the city proper, on the suburban peripheral of the community, Ingress agents cruise around at night, drinking beers and capturing portals in groups from their car windows.

How about D Skully from the South Bronx? He and that girl he confronted, an agent named VodkaNotWhine, became friends in the year that followed. They attended the same bar crawls and karaoke nights.

Agents also travel. Niantic regularly hosts "anomalies" — regional events where players from around the globe descend on a single city for a day-long assault. Local factions from around the country might send small groups, with local leaders coordinating their respective team and lending their collective firepower. Anomalies draw hundreds of carpooling Ingress players at a time.

A group of players meet in Philadelphia to coordinate before a Niantic-sponsored event. Players were organized into small teams and specific roles while a group of strategists watched the live map of the territory remotely and gave advice. Jack Smith IV/Mic

This is how Ingress players become so connected to their gaming environment — that is, the world around them. Since Ingress requires a lot of movement, and portals are tethered to visible landmarks, players incidentally end up discovering their neighborhoods in a new way.

It's all about exploration: Mic spoke to players who used Ingress while on vacation in Europe and Asia to get to know the neighborhood while fighting for their factions. Discovery is at the core of why Hanke, who previously lead the team behind Google Earth, built Ingress in the first place.

"The classic Google Maps experience is really about navigation, but how do you unearth little gems in a neighborhood?" Hanke said. "The [Ingress] game mechanic is there as an incentive, and it nudges people to get out, meet new people and discover new places."

Most recently, Niantic added a feature to Ingress that allows players to build and submit missions for other users. Visit neighborhoods like Sunnyside, Queens, and Ingress will take you on an objective-based walking tour of local landmarks and lunch spots; you can explore the real world while scoring for your faction.

In East Harlem, one player has used Ingress' mission-creation feature to build gamified guides to discovering the forgotten storefronts, churches and places of worship in the neighborhood — places that would be easy to overlook if your head were in your phone for any other reason.

Ingress is one of the earliest popular example of "augmented reality." Where virtual reality gives us goggles so that we can see an entirely different world, augmented reality uses cameras, phones, tablets and goggles to add things to the world we live in.

Google Glass, which could do things like translate street signs into your native language or overlay map information in front of your eyes as you traveled, was a largely unsuccessful first pass this concept. But a number of other AR experiments have popped up in the past year or so: U.S. Marines recently used augmented reality glasses to turn a golf course into a battlefield so that they could train in safety; Jaguar showed off a hypothetical car windshield that could overlay navigation and hazard information as you drive.

The next wave of augmented reality: Niantic Labs is planning on launching a whole series of AR games in the next year. But augmented reality has the potential to grow beyond gaming: It could affect labor, the economy, shopping and even education.

Intel recently debuted a line of 3-D-camera-enabled devices that let you see and manipulate digital objects in real spaces. It's easy to imagine a small group of children in a classroom looking through glasses and seeing the solar system in the middle of the room that they could navigate, explore and manipulate, right there in front of them.

"When we started Niantic Labs, the heads-up display in Iron Man was an inspiration," Hanke said. "In our vision of the future, that's what's going to happen, because it's so incredibly useful to have annotations about the real world available to tell you who likes that restaurant or what the history of a building is."

But for the agent Daniel, Ingress doesn't resemble some radical technological future so much as it does the past. Ingress is the way he remembers New York City in the 1980s, when people were out on the streets without phones, making their presence known and leaving a mark on the city.

"When I throw up a control field, it's like throwing up a 14-foot graffiti burn on the side of a building," he said. "It's me, representing my presence in this world. Here."