The free-form Lego-like game has sold more than 1.75 million copies, transcending the idea of purely "indie" success

By Chadwick Matlin

When Markus Persson was a teenager, a teacher asked him to think about his future. He responded with a jokey list "of things I wanted to accomplish before I was 30," he says. "The last couple of items were, 'Work as a game developer' and 'Become a millionaire.' "

He's a year late, but he can now put check marks alongside both. Persson, 31, is the lone developer behind Minecraft, a no-frills video game that has sold more than 1.75 million copies. If it hasn't quite reached the status of major hits such as Call of Duty: Modern Warfare 2, which has sold 14 million copies since its 2009 release, it also hasn't spent a dime on marketing. And unlike iPhone bestsellers such as Angry Birds, Persson's game hasn't enjoyed the distribution might of Apple or any other company.

The only place to buy Minecraft is on Persson's website, where it goes for €15 ($21). The game is played through a Web browser and puts users inside a vast, pixelated landscape. The goal, as much as there is one, is to avoid being eaten by monsters that come out after dark. But all the fun lies in building elaborate edifices to protect against those bumps in the night. Players use square blocks of materials like dirt, gravel, and clay to construct caves, towers, and fortresses. It's like playing with digital Legos.

That simplicity appeals to fans who use the game's building blocks to create art. One user designed a microprocessor within the game; flip a few switches, and it solves simple equations (1.35 million views on YouTube). Another built the exoskeleton of Star Trek's U.S.S. Enterprise and invited other players to help flesh out the interior (3.44 million views). The fans' devotion is so intense that the studio producing the Minecraft documentary was able to raise $210,000 from more than 3,000 contributors to make the feature film.

Persson coded Minecraft on a lark in 2009, looking for a side project when he came home from working his day job at King.com, a gaming site. By the end of January he was selling about 7,000 copies on an average day. "Once it got up to 15 copies a day, that was enough for me to have a salary. After that it's been like imaginary numbers," Persson says. The Independent Games Festival awarded its grand prize to Minecraft in March, though the game has done so well in the marketplace that "it starts to transcend the idea that this is purely an 'indie' success," says Brandon Boyer, IGF's chairman.

In late 2010, Persson founded a new gaming company in Stockholm called Mojang ("gadget" in Swedish). He and seven employees split their time between continuing development of Minecraft and working on a new video game, Scrolls, which Persson says will be a mix between the classic board game Risk and the fantasy card game Magic: The Gathering.

Minecraft follows in the tradition of other indie-game hits such as Crayon Physics Deluxe, which asks players to maneuver a ball by drawing ramps and other objects. Before deciding to sell the game on his own, Crayon creator Petri Purho talked to a publishing company about a marketing and distribution deal. "The money was very little that they offered, and on top of that they wanted to own basically everything about the game," Purho says.

Yet there are advantages to having a partner. Mojang plans to create versions of Minecraft for iPhones, iPads, and Android phones that will be available later this year and make use of third-party app stores such as Apple's iTunes. That might make Minecraft a little less "indie"—and potentially a much bigger hit.

The bottom line: Indie Minecraft sells 7,000 copies a day, enabling its developer to hire employees and expand the game to mobile phones and tablets.

Matlin is a Bloomberg Businessweek contributor.