Four-year-olds play it. So do 60-year-olds.
It's a welcome diversion for middle-aged commuters and routine entertainment for teenage students.
The mobile video game Temple Run has become a prime pastime for millions, and late last month, it hit a rare milestone: 100 million downloads.
Its vibrant graphics (such as bizarre-looking monkeys that chase treasure hunters) and simple game controls (players swipe their fingers on the screen or tilt the device to make a character run) make Temple Run a unique, often addictive activity for smartphone and tablet users.
While the game has its share of virtual surprises, including booby traps and road obstacles, there's another unexpected element related to this hit: It was created by Imangi Studios, a tiny development firm that has only three employees: husband-and-wife founders Keith Shepherd and Natalia Luckyanova, and artist Kiril Tchangov.
That small size is by design. "There is a strength to being a small business," says Luckyanova, 30. "We're very nimble."
Without layers of management, they can quickly change gears on a project or react swiftly to feedback from game users, she says.
For instance, when the company saw on social media that real-life athletes were playing Temple Run, they moved fast to create the character of Zack Wonder, a treasure hunter and star football player.
While Temple Run first launched as a pay-for-play game at 99 cents a download, company founders realized within a few weeks that they could significantly boost their user base — and potentially increase revenue — by switching to the "freemium" model. Under that approach, the game is free, but users use real money to buy virtual gold coins that can be exchanged for game upgrades.
Doing it all in house
Since its 2008 inception, Imangi has launched eight games, with Temple Run the most well-known. The company wouldn't disclose revenues for the game, which launched a year ago, but says it is in the millions.
Temple Run's popularity brought Imangi Studios to the attention of big-name companies seeking partnerships and licensing deals.
In June came Temple Run: Brave, a similar video game that features characters from the Pixar animated film Brave.
In coming months, there will be print and digital comic books featuring Temple Run's evil monkeys and its treasure-seeking adventurer characters. By the holiday season, store shelves will hold Temple Run card and board games, plush toys and apparel.
But success hasn't come easily. It takes long hours of intricate programming to create a video game. The Imangi Studio team has done everything from creating computer code to voicing sound effects.
"There wasn't any work-life balance to speak of. It kind of was all work," says Luckyanova — but the work is "fun" she adds.
Shepherd and Luckyanova, who had baby Katherine in June, say they will have a bit more balance now.
Prior to Temple Run, Imangi Studios had some smaller-scale achievements with the creation of games such as the ship-themed Harbor Master. But it's had setbacks, too.
A big one: taking too long to produce a sled-themed game. The founders hoped to have Little Red Sled on the market by the 2008 holiday season, yet they couldn't get it out until February 2009.
"We missed Christmas by a long shot," says Shepherd, 33. "It was a complete disaster for us. We definitely took on more than we could chew."
They also stumbled with Max Adventure, a then-99-cent game that has a boy saving the planet from aliens.
"We had spent a full year making this game, and it's not coming close to reaping back our investment," says Luckyanova. "So that was tough."
After reviewing what went wrong, they realized the game play and controls were too complicated for their target market of casual players on the go.
"We went to more of a gamer game, where you'd play at home on a console and you needed a joystick," Shepherd says. "It wasn't great for the mobile space."
Keenly aware of their missteps, they knew not to repeat them with the creation of Temple Run.
"Out of our biggest failure we created our biggest success," Luckyanova says.
Temple Run is easy to use for the casual gamer. Players use simple controls to navigate a treasure-stealing character through an Indiana Jones and the Temple of Doom-like maze.
Yet, it has built-in challenges. That character has to outrun "evil demon monkeys" while avoiding trees, fires and pits. As players advance, the game speeds up and obstacles get tougher to avoid.
"Its appeal lies in the fact that it's a pretty simple game to grasp but a difficult one to master," says Philip Michaels, editor of technology-focused website Macworld.com.
Users can build up points with speedy "runs" through the temple and by collecting gold coins. Similar to arcade games, there is a focus on getting a brag-worthy score, which can easily be shared via an in-game Twitter icon.
Many players post screen shots of their scores on Facebook .
"It's not just the same old thing," Michaels says. "They really managed to tick off a lot of the boxes that make for a successful casual game."
It got rave reviews and an average of four-and-a-half out of five stars by the 1.4 million people who ranked it on Apple's App Store .
Its also won praise on social media from big-name celebrities including singers Justin Bieber and Mary J. Blige and Miami Heat basketball star LeBron James.
One Tweet from James: "Man I'm seriously addicted to #TempleRun #GameApp."
Mobile games exploding on scene
Imangi Studios has successfully infiltrated an industry that is bulging with business potential.
There will be 94.6 million mobile gamers in the U.S. by the end of the year, according to estimates from research company eMarketer. It says that number will rise to 138.3 million by 2015.
But the money-making opportunities also lure competition.
"It's a very crowded market," says Macworld.com's Michaels. "For every Temple Run, Angry Birds or Words with Friends, there are dozens upon dozens of games that never get on anyone's radar."
The Imangi Studios founders are well aware of the rising rivalry. When they launched their first game in July 2008, there were about 500 selections on the App Store. Now, there are more than 500,000.
"It's very, very competitive," Shepherd says. "In some ways, I think it's harder to be more successful than when we first started."
In turn, the founders have made some adjustments to their business structure.
While they want to keep the firm small and manageable, they've begun to work closely with others, such as three independent contractors — a developer, an artist and someone to help with customer support — and professional law, accounting and branding firms.
"You do have to let go a little bit and find partners that you are confident in," Shepherd says.
They're keeping some things the same. Shepherd and Luckyanova will continue to work from home in Raleigh, N.C., while artist Tchangov works in Richmond, Va.
Luckyanova says they don't need to rent expensive office space or jet around the world. They want to be conservative and level-headed.
"Temple Run is a huge hit, but our next big game may not be such a big hit," Shepherd says. "We don't feel like it would be a smart move to act like this money will last forever."
There are other business practices Imangi Studios doesn't plan to change: constant innovation, examining its failures and always moving ahead.
"There's a history for us of trying differing things, not always succeeding and learning from our mistakes," Shepherd says. "We just keep trying and don't give up."