What is sudoku?

Sudoku  is a unique logic-based, combinatorial number-placement puzzle. The goal of Sudoku is to complete or fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 sub-grids that compose the grid (the boxes) contains all of the digits from 1 to 9.

Completed puzzles are always a type of Latin square with an additional constraint on the contents of individual regions. For example, the same single integer may not appear twice in the same 9×9 playing board row or column or in any of the nine 3×3 subregions of the 9×9 playing board.

Other versions of the classic 9×9 Sudoku grid are 4×4, 12×12 Sudoku or even 16×16 Sudoku (with letters included).

The puzzle was popularized in 1986 by the Japanese puzzle company Nikoli under the brand Sudoku which means single number. Sudoku became a global hit in 2005 and still today, many people complete their daily Sudoku online or in their favorite newspaper.