Sudoku is a logic-based combinatorial number-placement puzzle introduced by the Japanese puzzle company Nikoli in 1986. The objective is to fill the 9 x 9 grid with all the digits from 1 to 9. The trick is the entire block is a 9 9 x 9 grid and that each grid and horizontal and vertical line must contain the digits 1 to 9 with no repeats. Each puzzle gives you several numbers in each grid to get you started.
Sudoku swept into the worldwide spotlight circa 2005. Who do we have to thank? New Zealander and retired Hong Kong judge Wayne Gould. In a Japanese book shop Gould caught sight of a partially completed puzzle in 1997. Over the next six years he developed a computer program to produce the puzzles. He sent a puzzle to The Times newspaper in Britain, which published a Sudoku puzzle for the first time on November 12, 2004. The first U.S. newspaper to feature a Sudoku puzzle was New Hampshire’s The Conway Daily Sun in 2004.
If you’re wondering, sudoku means “single number.”