It's midafternoon on a summer day, and Olivia Prokopová stands on a practice green in her backyard, putting golf balls across a 15-foot (4.6-meter) faux-grass fairway, up a 45-degree red tin ramp, toward a hole suspended two feet off the ground. "Watch your stroke!" her coach says. "Slowly. Don't rush."

She lifts her putter, listening, puts her head back down, draws the club steadily back and swings. Two of the next four shots roll straight into the hole.

At just 10 years old, Prokopová is the wunderkind of miniature golf. She entered her first U.S. Open at 7. At 8, she led all players, adults included, for 72 holes at the World Crazy Golf Championships in England.

She practices an average of five hours a day and has set her sights on winning the U.S. Pro Mini-Golf Masters.

"I need to perfect my stroke," she said. "I need to get better at adjusting to weather."

Invented in 1916, mini golf reduces the standard game of golf to its last few dozen feet. Although obstacles such as mock windmills may make mini golf seem like child's play, many courses have done away with comic hurdles in favor of carefully designed banks and ramps. Professionals say it requires as much skill as billiards.

Born in Rakovník, central Bohemia, Prokopová seems like an unlikely mini-golf star. Many Czechs have never even picked up a putter, and the country has only about 20 tournament-worthy courses. Her parents say she fell in love with the sport at age 4 and has wanted to play it nearly every day since.

In clamdiggers two sizes too big, an oversized baseball cap and a polo shirt emblazoned with sponsor logos, Prokopová cuts an odd and imposing figure on the pro mini-golf circuit. She plants her legs wider than most golfers, who prefer them in line with their shoulders, and holds her putter with hands apart instead of the standard interlocking grip. But many adult golfers work years to develop a stroke as smooth as hers. And her demeanor is famously cool. As she lines up shots or strolls from one hole to the next, her freckled, chubby-cheeked face wears the spooky self-confidence of a child who plays an adult game — and often beats the adults.

She doesn't follow the leader board and she doesn't talk to opponents.

"One player complained that Olivia was quiet," said her father and manager, Jan Prokop. "She doesn't speak much English for one thing. But even if she did, she wouldn't talk. Olivia comes to play mini golf, not to make conversation. She's a professional."

Prokop, a friendly chain-smoker with an enormous beer belly, is a chatty counterpoint to his quiet, steely daughter. He is too nervous at tournaments to see "more than a fifth" of Prokopová's shots, despite taking her to four tournaments a year in the United States.

"Our favorite place is Myrtle Beach," said Prokop, who wears an American-flag belt buckle, carries a red, white and blue mobile phone, and has a bald eagle painted on his car hood. "The beaches! The sea! All those mini-golf courses!"

Prokop's zeal for the United States partly explains his daughter's transformation from a prodigy in a sport no one in her country much cares about into a child pro on the U.S. tour. In 2001 a Czech mini-golf developer invited her to a tournament in Austria. A week later Prokopová received an invitation to compete in the U.S. Open of Mini Golf, where she championed the under-12 category and placed fourth among women overall.

After that, her father quit his job at a newspaper and took up freelancing so he could escort her abroad whenever tournaments called. He traded in a spacious apartment for a run-down, boxy house — but with a backyard, so he could build a three-hole practice course.

Prokopová misses about half of her school days because of mini golf, but she still earns straight A's. Her father acknowledges that in a way, she "doesn't have a childhood." But, he adds, "Did Jágr have a childhood? Do Olympic gymnasts have childhoods? How many 10-year-olds have met the president?"

"It's strange," Prokopová says, pausing to consider. "I live in two worlds: the world of adults and the world of children. I like them both. Maybe I like kids better. They are more fun."

She spends an average of five hours a day putting in her backyard but sometimes practices as many as 12 hours. Three times a week her coach, 1998 Czech mini-golf champion Marek Spidra, joins her.

"There's no one else in Europe, child or adult, this devoted to the sport," Spidra said. Gary Shiff, a mini-golf pro and vice-president of the U.S. ProMiniGolf Association (PMGA), said, "Olivia may put in more mini-golf hours than anyone in the world. ... She's easily the best junior player, one of the best women, and she can hang with the big boys."

Prokopová routinely beats half the field at U.S. PMGA tournaments. She has twice finished in the top 10. Her best performance came at the 2003 World Crazy Golf Championships in England. ("Crazy" golf courses have novelty obstacles, such as windmills; PMGA courses have natural obstacles, such as rocks and slopes.) After four rounds at the England tournament, she led the pack. She ended up in third place, with a score of 279 strokes on 144 holes.

Prize money at mini-golf tournaments maxes out at a few thousand dollars. Last year, the family spent 700,000 Kc ($30,000) to take Prokopová and her coach to seven tournaments abroad. Half the money came from sponsors, mainly companies in Rakovník. Prokop and his wife paid the rest.

Even the best mini golfers have day jobs, but can earn tens of thousands of dollars in sponsorships, endorsements and winnings.

"Why shouldn't she be able to make a living at it?" asked Prokop. "Prize money gets bigger each year. All she needs is one big sponsor."