Do you sudoku?

TO ITS fans, it is addictive. To the media, it is a promising money-maker. Sudoku, an old puzzle long popular in Japan is fast gaining popularity the world over. In Britain, a sudoku book is a bestseller and national newspapers are competing feverishly to publish the most, and the most fiendish, puzzles. (Last week the Guardian printed a board on every page of one day's features section.) Meanwhile, the puzzle is being published in newspapers from Australia to Croatia to America. The Japanese buy more than 600,000 sudoku magazines a month. Even the New York Times is considering introducing sudoku in its Sunday magazine, alongside its venerated crossword.

The game's appeal is that its rules are as simple as its solution is complex. On a board of nine-by-nine squares, most of them empty, players must fill in each square with a number so that each row (left to right), column (top to bottom) and block (in bold lines) contains 1 to 9. (A sample accompanies this article; the solution appears here.) Advanced versions use bigger boards or add letters from the alphabet.

Sudoku—the Japanese word combines “number” and “single”—seems perfectly suited to modern times, a puzzle for an era when people are more numerate than literate. And like globalism itself, sudoku transcends borders by requiring no translation.

The overall business of puzzles is hard to measure, but revenues in America from magazines, syndicated newspaper sales, books, and online and phone services are almost $200m annually. The New York Times earns millions of dollars a year from its crosswords and hundreds of thousands from a special phone service that provides hints. Over 30,000 people pay $35 a year for the newspaper's e-mail version, says Will Shortz, the crossword-puzzle editor.

For now, sudoku revenues are more modest. The person who supplies most western papers with the puzzle—Wayne Gould, a retired Hong Kong judge—does so for nothing, to promote sales of the sudoku software he developed, initially for fun. He says that if trends continue he may earn $1m this year from software sales and book royalties. Michael Harvey, features editor of the Times of London, which first published the puzzle in November, thereby setting off Britain's sudoku craze, claims that the grids have brought many new readers to the paper.

Puzzles have long been popular. A word square dates from 1st-century Pompeii. The crossword puzzle was launched in the New York World in 1913. After a compilation appeared in 1924—the first book by Simon & Schuster—the genre exploded. It is now a daily staple for millions of people worldwide.

Will sudoku, whose origins lie in an 18th-century Swiss mathematician's game called “Latin squares”, follow suit? Might it even prove to be the disruptive technology that kills the crossword? In the battle between left-brain and right-brain people for puzzle primacy, crossword aficionados defend their squares, noting that word puzzles offer more variety of themes, sizes and skill levels. “It is not obvious how you can vary the [sudoku] puzzle to make it more interesting”, says Mr Shortz. “It is what it is”.