Mr. Kaji and the company have had a hand in creating and promoting most of the half dozen or so number puzzles that have taken off after sudoku. But Mr. Kaji says that Nikoli has at least 250 more puzzles like sudoku, the vast majority of them unknown outside Japan.
Nikoli�s secret, Mr. Kaji says, lies in a kind of democratization of puzzle invention. The company itself does not actually create many new puzzles � an American invented an earlier version of sudoku, for example. Instead, Nikoli provides a forum for testing and perfecting them. About 50,000 readers of its main magazine submit ideas; the most promising are then printed by Nikoli to seek approval and feedback from other readers.
That process allows Nikoli to tap into the insatiable urge of Japanese puzzle solvers to tinker and improve, a drive its readers apply to games with the intensity of Toyota�s engineers trying to outdo Detroit�s automakers. Most of Nikoli�s games are original, says Mr. Kaji, but a few, like sudoku and kakuro, are improved versions of older games invented elsewhere.