Quiet intensity at Fifth World Sudoku Championship

You hardly knew you were in the middle of Center City on Friday afternoon, at the Juniper Room of the Courtyard Marriott, across from City Hall. There, a quiet intensity shut out everything else at the Fifth World Sudoku Championship, where 120 of the world's best Sudoku solvers from 32 countries were competing in individual and team play.

Contestants for the first five rounds - all individual competition - sat at two-person tables, divided by yellow cardboard barriers in the middle. Each place had a sheet with a flag, and no table had the same two flags.

"For the individual rounds, we scattered the flags around the room," explained Will Shortz, the New York Times puzzle editor and puzzle-master of NPR's Weekend Edition on Sundays. "You can sit wherever you see your flag, but you'll be sitting nowhere near anyone else on your team."

Shortz is host of the competition, as well as the national championships The Inquirer has sponsored since establishing them three years ago.

Over the two days of solving, contestants from around the world are competing in rounds laid out much like the decathlon in the Olympics: 10 different events to challenge different skills.

They assembled to begin the first round at 1:15 p.m. Friday - eight classic Sudoku puzzles that puzzle constructors Thomas Snyder and Wei-Hwa Huang, both former national champions for the United States, called the "100-meter dash." The solvers had 20 minutes to complete all eight, Sudokus that are much the same as those that appear in newspapers daily, including both The Inquirer and the Philadelphia Daily News. Only one solver - Jakub Ondrousek of the Czech Republic - finished all the puzzles, and all correctly. The Czech team is considered one to watch this weekend.

The solvers took a quick break, then returned to the room for the second round - "the long jump" - seven puzzles with major twists, such as circled cells that must equal the sum of all the digits in an arrow's path inside a Sudoku grid. That round lasted 40 minutes, and no one finished all the puzzles. And so the day went: a 40-minute "shot put" third round with odder-looking grids, one like a parquet floor; a 35-minute "high jump" with some puzzles completely empty except for numbers outside the grid; a 35-minute "400 meters" with eight standard puzzles that demanded tough, advanced solving strategies.

The late-afternoon rounds were for team-solving puzzles - one a complicated set of six Sudoku that had to be solved by placing colored stickers on the grid, with 90 seconds allotted for each puzzle.

Godfrey Cheng of Toronto, competing on the Canadian team, said after one of the rounds that the nonstandard Sudokus were more familiar to competitors from overseas. "We're not used to the variants," he said, although he had played them in a booklet of practice puzzles for the championship. "These are not only variants, but a hard version of the variants," Cheng said.

"One thing's for sure - this contest separates the elite guys from the really good guys. There's going to be no ambiguity about who the champ is."

In last October's national championship, which was held at the Convention Center, a third-place winner was suspected of cheating and eventually was stripped of his $3,000 prize after doing poorly in a retest. The player had competed in elimination rounds and may have concealed, under the hood of a sweatshirt, an electronic device that aided him. This time, tournament officials say they are more alert to the potential for cheating, but with no prize money on the line, there is less incentive to cheat.

In this competition, players receive points for all puzzles completed correctly within rounds; failure to finish a round does not disqualify a solver. In team play, up to three members of each national team compete on puzzles; many teams wore distinctive shirts Friday, announcing the countries they represented. Individual and team scores are totaled to determine the national champs. On Saturday, the five individual solvers with the top scores compete against each other in a lightning-speed hour of Sudoku, with 10 puzzles, to determine the world champion.

The six-member U.S. team includes Tammy McLeod, a Google programmer from Los Angeles. She won $10,000 in the national championship here last fall and also a seat on the world championship team, where the prizes are trophies.

The language of the competition is English, although none of the Sudokus has any words associated with solving the puzzle. Solvers have been practicing on workbooks with Sudokus, including examples of all their variants that appear in the competition, for weeks; most competitors understand English but had the time to get explanations of the odder games translated into their own tongues during the last week's individual practice period.

When play broke between rounds Friday, the hallway on the mezzanine of the Courtyard Marriott was a polyglot of different languages from solvers, many of them apparently reviewing the relative difficulty of the puzzles.