Who is Seth Priebatsch? How did his tiny company, based on turning life into a video gaming experience, wind up with a $100 million valuation?

Seth Priebatsch, left

FORTUNE -- As I walked through the front door of SCVNGR in Cambridge, Mass., a $100-million company that makes location-based apps to rival Foursquare and Groupon, a painted canvas of the cover of Ayn Rand's "Atlas Shrugged" greeted me. Standing beside it was the the man who hung it there, SCVNGR's CEO -- ahem, "Chief Ninja" -- Seth Priebatsch. He was not wearing shoes.

No reason to put on shoes when you're walking around your apartment, which is what the office is to Priebatsch. He spends every night there, pulling sheets out of a desk drawer like he's Don Draper grabbing a fresh Oxford. He doesn't have an apartment, he says. "If I need laundry done, I outsource my laundry to my parents, it's very efficient. They get to borrow the board room, and I don't have to figure out how the hell the laundry machine works."

As you've likely gathered, Priebatsch is 22 years old. He's also worth millions. And not just because he's had a "Projects" folder on a hard drive since he was 8, made tens of thousands of dollars every month on a startup when he was 16, and dropped out of college after freshman year. He's the man in charge because he sensed something three years ago that most of the rest of us did not: that a generation raised on video games would want to keep playing a game in real life. "I found out that basically the real world was essentially the same game as Civilization [an old computer game], just with slightly better graphics, maybe, and slightly slower." More