Game fads have always come and gone, falling as surely as they rise, but Fortnite continues to act like it's never heard of gravity. At Epic Games' annual Game Developer Conference address yesterday in San Francisco, the company announced that its battle royale juggernaut had grown to 250 million registered players—up 25 percent in just four months. Epic also showed off a number of improvements to its widely used game engine, Unreal 4, and announced a number of new exclusives coming to its new PC game store.

What got lost amid the headlines, though, was that Epic—both with Fortnite and through companies like Magic Leap using Unreal Engine to build mixed-reality AI characters—is shaping our virtual future in subtle but surprising ways. After the company's address, we sat down with Epic CTO Kim Libreri and founder and CEO Tim Sweeney, long a backer of VR and other immersive technologies, to discuss their vision for a million-person connected experience.

WIRED: Epic has been around for nearly 30 years, but over the past year and a half it seems like the rest of the world has come to think of it for one thing and one thing only, and that's Fortnite. Does that ever feel reductive?

Sweeney: Fortnite's the only game we've had with this magnitude of success at all. It's kind of unprecedented in a lot of ways, but it's a culmination of all the things we've done—with our engine, our services, and all the other elements we've been working on for decades. It's wonderful to see it come together in this way that feels like something you might see in the metaverse in the future.

How early did that begin to emerge as an intention for the game—not just to create mystery through the narrative, but to branch out and use it as a metaverse of sorts?

Sweeney: As with most things at Epic, players had already done it by the time we recognized it was happening. Creative Mode, where players can go and create their own island and build their own work, including collaboratively with others, is now driving a large number of players. They're building maps, they're sharing them with friends, and we're seeing more and more new types of gameplay emerge from that. It's taken on a life of its own, and I think that's going to be the driving force for Fortnite in the future.

You and the rest of Epic have been early backers of immersive technologies since VR resurfaced in 2012. Do you think of Creative Mode explicitly as a test bed for an age when this might be a more embodied play experience?

Sweeney: Oh, absolutely. This is the wonderful part of Epic and Fortnite. Every week we release a new update with more development work towards what we think is going to be the foundation of the future. Some weeks we're right and we advance the game; some weeks we're wrong, but it's always making progress in a bunch of different directions simultaneously. The Marshmello concert was a real marker that showed how far we've come in going beyond just being a game experience, but it's just the very beginning—and that was a heavily produced partnership between Epic and Marshmello. In the future, things will become more and more achievable without Epic even being involved.

Libreri: To truly see the future of collaborative gameplay and social experiences, you need a large-scale community to help that happen. This idea that a computer programmer in a basement invents the metaverse, it's just not true. We need a planet full of people to really help guide these things.