Nikoli, the Japanese publisher that turned sudoku into a blockbuster, has about 250 more where that came from, most of them unknown outside Japan. Founded by a college dropout with a horseracing habit, the company doesn't invent puzzles, it relies on its readership to submit ideas, as well as help test and perfect them.
It's the Japanese enthusiasm for number puzzles—since the written language's complexity renders word puzzles impractical—that fuels Nikoli's success. “We’re prolific because we do it for the love of games, not for the money,” says the company founder, who points out that they lost the potential to make a fortune by not trademarking sudoku. It's a model, he says, they'll continue.