From inside the cave, I turned and approached an opening that looked out upon a ridge high above the shore. “What happens if I jump off?” I asked.

“You’ll be fine,” he said. “We didn’t want you to break your legs and get hurt. It is about exploring. We didn’t want people feeling nervous.”

Each planet had a distinct biome. On one, we encountered a friendly-looking piscine-cetacean hybrid with a bulbous head. (Even aggressive creatures in the game do not look grotesque.) In another, granular soil the color of baked salt was embedded with red coral; a planet hung in the sky, and a hovering robot traversed the horizon. “Those are drones,” Murray said. “They will attack you if they find you killing animals or illegally mining resources.” On a grassy planet, doe-eyed antelope with zebra legs grazed around us. Mist rose off the grass as I headed down a ravine shaded by trees. “This is a place where no one has been before,” Murray said. The biome was Earth-like in light and in color, naturalistic. As I descended, the ravine deepened until rock façades took shape on either side. In spite of the work’s semi-finished state, the world was absorbing. “I’m sorry there’s no game-play element on this planet yet,” Murray said. His mind turned from the screen in front of us—the six planets, tidily assembled for the demo—to the full version of No Man’s Sky on the operating table on the studio’s first floor, below us. Until many improvements were fully realized, the whole of it would inevitably look worse than what we were seeing. “You can lose sight that it once looked like this,” he said.

This version of the game—a frequent reference point for the studio—was a reminder of a public promise: the presentation that Murray had given at E3, where he stood on a huge stage with images of No Man’s Sky projected onto ninety-foot screens. “There were five thousand people in the audience, and at least five million watching at home,” he told me. “I sat backstage, and, before walking out, I had a feeling that I could go to sleep—just turn around and go.” One of the studio’s programmers who was with Murray backstage recalled, “Sean got whiter and whiter—he was just catatonic.” To overcome his nerves, Murray focussed his mind on the story of the game, beginning with the studio’s origins. He told me, “By the time I walked out, I could have burst into tears, because what I was going to say was that this is basically the game I’ve always wanted to make.”

Murray’s earliest memories are of life on a cane farm in Brisbane, Australia. He was born in Ireland, but his parents migrated to Australia when he was two years old. “We basically lived in a glorified shed,” he told me. “It was up on stilts, and it had a corrugated-iron roof.” Two years later, Murray’s parents moved again, to work on a remote million-acre ranch in Queensland. The settlement resembled an alien outpost, with its own power-generation system and its water pumped on-site. Visitors who wanted to avoid a four-hundred-mile drive on a rutted track had to fly in. (The ranch had seven airstrips and an abandoned gold mine.) Dust storms swept across the desiccated soil. Merely crossing the property was like an expedition. “You would go out to check that the windmill, or whatever, was working,” he said. “And you always had to go out in twos. As a kid, you were told that, if something happened to the person you were with, then find some shade, and if there is no shade don’t go looking for it. You will survive for three days without water and without food, and so you have only one job: gather kindling to light a fire. You stay exactly in the same place, and you light a fire at set times, and that’s it. There is a plan: we can fly over, and in three days we can cover the whole grid.” Murray often accompanied his father on multi-day treks. At night, they camped under pristine night sky, with all of space arcing above them.

In the outback, Murray became fascinated with sci-fi. When he first encountered “Dune,” he said, “I can remember being hungry reading it, forgetting to eat.” Years later, when he formed Hello Games, he told his co-founders—two coders named Ryan Doyle and David Ream and an artist named Grant Duncan—to consider their childhoods as source material for games. “I said, ‘Think back to when you were a kid. What did you want to be? A cowboy, an astronaut, a stuntman, a fireman, a policeman, whatever.’ ” Working in Murray’s living room, the four men at first devoted their attention to fundamentals, writing software to determine how objects would behave in a theoretical game space. “We mentioned Pixar a lot, because their work is colorful but not childish,” Duncan told me. The inspiration for Joe Danger came from a stuntman figure that Duncan found in a box of old toys.

The partners worked for a year, and went nearly broke. “I had sold off my PS3,” Murray told me, referring to his PlayStation. “We were down to the bare essentials.” For the release, in June, 2010, Murray bought some cheap cider. “We decided, we are going to drink cider, and it will come out and do what it will do,” Murray said. The game did not appear online in the United Kingdom until after midnight. When it first loaded, the screen was black, causing momentary panic. But within an hour the partners had made back their money.

Murray started No Man’s Sky one morning two years later, during a difficult negotiation with Microsoft over the marketing for Joe Danger’s sequel. “Everyone else was at home,” he recalled. “I was in the studio on my own, and I just started programming. I was furious, and I kept working until three in the morning. Looking back, I think I had the equivalent of a midlife career crisis. What is the point of these games? Like, Joe Danger—how impactful is it?” Murray and his co-founders had joked that they would one day make an ambitious game, which they called Project Skyscraper. The following day, he told Duncan and Ream, “We’re doing it.” He had created only a small patch of sample terrain, without a clear sense of what it would be, and Ream told me, “The thing was quite abstract, and we were like, What are you doing?” Duncan was skeptical. Artists he knew were dismissive of the technique that Murray was using; one had warned him that the results “look like shit.”

Duncan and Ream began to design a relatively conventional game, in the mold of Joe Danger—another humorous take on a childhood dream profession. Their working title was Space Cadets. But Murray urged them to consider the project in more open-ended terms. “I had this feeling: I want to start a new company, like almost an alternate path for Hello Games,” he told me. He split his company into two, and for months the three men, along with a coder named Hazel McKendrick, worked on No Man’s Sky in secrecy, in a locked room.

To build a triple-A game, hundreds of artists and programmers collaborate in tight coördination: nearly every pixel in Grand Theft Auto’s game space has been attentively worked out by hand. Murray realized early that the only way a small team could build a title of comparable impact was by using procedural generation, in which digital environments are created by equations that process strings of random numbers. The approach had been used in 1984, for a space game called Elite, which Murray played as a child. Mark Riedl, the director of Georgia Tech’s Entertainment Intelligence Lab, told me, “Back in those days, games had a lot of procedural generation, because memory on computers was very small; it was largely forgotten, but now it is being rediscovered.” (Minecraft, an expansive world that was designed by only one person, also uses the technique.) Games based on procedural generation often suffer from unrelenting sameness, marked by easily detectable algorithmic patterns (imagine a row of more or less identical trees, stretching to infinity), or from visual turmoil. But Murray hoped that if a middle ground could be achieved he could create graphically rich environments worthy of discovery—a fictional version of exploration that had a grain of reality to it.