OULU, Finland— Toni Fingerroos may seem a little out of place in the vibrant Nordic startup scene.

When the 29-year-old computer programmer launched a mobile game called "Hill Climb Racing" in September 2012, it lacked the usual whiz-bang graphics. He didn't have a war chest of venture-capital backing to fund a team of experienced developers.

And, having chosen to launch the game on Google Inc. GOOG +0.58% 's Android operating system, his company—Fingersoft Oy—lacked the closeness with Apple Inc.AAPL +0.01% that has helped propel other Finnish gaming companies, including "Angry Birds" maker Rovio Entertainment Ltd. and "Clash of Clans" maker Supercell Oy.

Still, by the end of 2013, Mr. Fingerroos's "Hill Climb Racing" had attracted more than 140 million downloads.

According to Fingersoft, the company had a net profit of €9.4 million ($12.7 million) on revenue of €15.5 million last year. Its revenue came from advertising sales and distribution of so-called in-app purchases, or upgrades users buy for an otherwise free game.

To compare Fingersoft with one of its heavyweight Finnish peers: Fingersoft achieved a net profit rate of 61% of revenue, versus Supercell's 38% in 2012, the most recent year for which figures are available.

In addition to distributing his own games, Mr. Fingerroos, who is the sole owner of Fingersoft, has expanded into publishing titles made by others, such as "Fail Hard," by Viima Games Oy.

Mobile gaming rags-to-riches stories aren't rare, and they are likely to multiply as people increasingly gravitate to smartphones and tablets for most of their information and entertainment needs. In the Nordic countries, where a generation of young gamers honed their programming skills during long, dark winters, companies like Spotify AB, "Minecraft" maker Mojang AB, "Candy Crush" maker King.com Ltd. and Supercell have racked up multibillion-dollar valuations and solidified the region's place as a development hub.

Mr. Fingerroos's story proves that loners still have the potential to succeed in an industry that is quickly maturing. His company is based in a house located in a residential neighborhood in Oulu, a Finnish coastal town about 350 miles north of Helsinki.

Oulu is one of the major R&D centers for the former mobile-phone giant Nokia Corp.NOK1V.HE +0.95% , and while Nokia's fortunes have declined, the city boasts a concentration of tech firms.

Today, Fingersoft is staffed by a dozen employees, working in confines more appropriate for frat boys than gaming executives. Its office features a white board with sticky notes and diagrams, as well as work stations with multiple computer screens.

But a big refrigerator stocked with beer, shelves lined with spirits and a pool table upend any resemblance to a corporate atmosphere. Work on Friday afternoons can segue into a casual sauna-and-Jacuzzi session, with employees downing a few brews.

Having fun is important at Fingersoft. "We believe it results in the best-possible products," Mr. Fingerroos said.

It hasn't always been fun and games. Fingersoft, in its current form, was born in late 2011 when its founder came to realize he was flat broke after pouring money into developing a game for Sony Corp.'s6758.TO -0.12% PlayStation. "We ran out of money, and I had accumulated some debt," he said in an interview at his office. "I had to choose between seeking a job and launching my own business."

He placed the bet on himself and began developing mobile applications for Android devices. Working alone, Mr. Fingerroos said, he designed a new app every couple of days with the aim of throwing his ideas against the wall to see if some would stick. "It's better to get 10,000 downloads for a lousy app than to have nothing out there," he said. In February 2012 he launched an app called Cartoon Camera, which allows users to make their digital images look like sketches or drawings. It marked a milestone for Mr. Fingerroos and his company.The art app quickly amassed more than 10 million downloads. It was a godsend for Mr. Fingerroos, allowing him to pay off debts and build his confidence.

He then set to work on "Hill Climb Racing." While its graphics are basic, the game requires finesse. Players must combine skillful braking and throttle control to guide two- or four-wheel vehicles on uphill climbs and descents in various landscapes.

Mr. Fingerroos is a self-taught programmer who didn't graduate from college. He started writing his own software at age 10. Even then, car racing was on his mind. "I wrote with QBasic programming language a racing game called 'Ralli 94,' " he said. Ralli is Finnish for rally.

He created the game that would make him a millionaire two decades later in a compact bedroom. Today, that room doubles as a nursery for his 7-month-old daughter and a reminder of the company's rapid ascent. Press clippings are tacked on a closet door, and two desks with computers appear to sit untouched.

Write to Juhana Rossi at juhana.rossi@wsj.com