To those who looked more closely, however,
Kashikoku Naru offered an additional layer of intrigue. It was Sudoku—with math—and,
thus, not Sudoku at all. Invented in 2004 and licensed from Miyamoto for use in a puzzle
book series by Japanese publishing behemoth Gakken in 2006, Kashikoku Naru books
had sold in excess of two million volumes by 2009. The puzzle had also journeyed
overseas—licensed and then launched with a newer and simpler name: KenKen (a.k.a.
“wisdom squared”).