Not long ago, I took Amtrak's Acela to Tokyo. Once there, I boarded a Shinkansen bullet train and was whisked to Kyoto, where I rented a car and, following neatly handwritten instructions, drove an hour northwest. When the suburbs gave way to craggy hills that were green with late-spring growth, I turned right down a rutted dirt road and parked my car near a roaring waterfall. The last nine miles of my journey were by ox cart along an uphill path that paralleled a rushing, mountain-fed stream.
At last I came to a wooden building, rustic but handsome and well made, reminiscent of a Shinto shrine. I had arrived at Sudoku Dojo, the ancient compound where sudoku number puzzles have been crafted by hand for centuries.
Sudoku -- the name translates, roughly, as "single number" -- is a logic puzzle that has long been enjoyed in the Land of the Rising Sun. Players fill in nine 3x3 grids so that the numbers 1 through 9 appear only once. The numbers may not repeat in columns or rows. The Washington Post recently started printing a sudoku not far from where this very column appears.
I am fortunate to be one of few Western journalists allowed into Sudoku Dojo. The exact location must remain a secret, lest it be overrun by sudoku addicts, who in their zeal to get the latest puzzle would ruin the contemplative atmosphere that is so vital to sudoku creation. (These so-called Sudokuheads are an increasing problem in Japanese cities, where they slump in coffeehouses and sushi bars, oblivious to everything but the latest puzzle.)
My guide for my visit was Akira Watanumba. He is a 12th-generation sudoku master. His father made sudoku. So did his father, and his father, and his father, and his father, and his father, and his mother, and her father. His father was a pachinko ball polisher, but his father made sudoku. (And so did his father.)
In short, sudoku is a way of life for Watanumba-san. He was dressed in the traditional sudoku master garb: black-and-white check kimono over silk drawstring pants, with toe socks on his feet and a green eyeshade on his head.
Eighty-one sudoku masters work at the dojo. Each is responsible for filling in a different box on the sudoku grid.
The process is started by the head sudoku master, Masahiro Ono. I watched as the gray-haired Ono dipped his boar's-hair brush into a tiny pot of ink then carefully turned it, removing any excess pigment. Clipped onto an angled drafting table in front of him was a large sheet of finest rice paper divided into many squares. He lifted the brush, paused for a moment with his eyes closed as if deep in thought, then neatly drew the number 8 in Box 1, the topmost square on the right.
The sudoku was underway.
Once the 8 was dry, a trainee unclipped the rice paper and carried it to the master in the next cubicle, Shigeru Ishihara. Each sudoku master has to decide which number to put in his box. (Or her box; the first female sudoku master, Shizuko Tanaka, was named in 1923.) Since Mr. Ono had just put an 8 in his box, that number was unavailable to Mr. Ishihara. Ishihara-san rose, consulted a few reference books that were piled haphazardly on a table behind him, then sat back down and boldly put the number 1 down in Box 2.
Of course, not every box is filled in. Some must be left empty or sudoku players would have nothing to solve. Whether to leave a box blank is one of the hardest decisions for a master to make. One of the greatest sudoku masters, Takadigit Daiko (1627-1701), never used his brush at all. He always left his box blank. Experts say you can instantly tell a sudoku that Daiko worked on. Today his puzzles are much prized by collectors, who will pay upwards of 100,000 yen for an original example.
And so the sudoku is created, box by box. It is a painfully slow process, taking exactly one day to complete one sudoku. Once the ink is dry on the final number, a trainee carries the rice paper to a tiny outbuilding not far from the main dojo.
"We are not so backward as you may think," Mr. Watanumba, my guide, said to me, opening the door. Inside was a flatbed scanner and a PC. The sudoku was scanned into the computer and converted to a digital file that was beamed to a satellite in geosynchronous orbit 22,000 miles above the Earth.
From there it was transmitted to newspapers all over the world, where it appeared the next day for your puzzle-solving pleasure.
As I boarded the ox cart for my journey home, Mr. Watanumba bowed to me and said, "We are honored that the humble fruits of our labors have brought joy to so many. Sayonara."
Your Number's Up
Of course, that's not really how The Washington Post's sudoku puzzles are created. They're actually the product of Wayne Gould, a 60-year-old retired law judge from New Zealand who lives in Hong Kong.
The basic puzzle dates to the 18th century and Swiss mathematician Leonhard Euler, who called his creation "Latin squares." In the late 1970s, American puzzle publisher Dell produced puzzles called "Number Place." These spread to Japan, where number puzzles are popular because the pictographic Japanese alphabet makes crosswords close to impossible.
Wayne saw a sudoku in a Japanese magazine and set about devising a computer program that could generate them. I asked him to describe how it works.
"Sorry, I can't do that," he e-mailed me back. "We get into the area of proprietary algorithms (otherwise known as 'trade secrets')."
Do you sudoku? My e-mail: firstname.lastname@example.org.