Sudoku

Sudoku is a game that challenges your logic and reasoning skills by requiring you to fill in a 9×9 grid with numbers 1-9 in a way that each column, row, and 3×3 box contains all of the digits. The game provides you a partially completed grid, and your task is to complete the rest of it.
Once you complete a game, you'll have created a unique Latin square, following various constraints, such that no number repeats within the same row, column or small 3×3 region. French newspapers played with variations of these puzzles centuries ago, but their wider popularity came when Nikoli, a Japanese puzzle company, started producing them in 1986 under the name Sudoku. This name, meaning "single number," stuck, and in 2004 it even made an appearance in mainstream media when Wayne Gould devised a computer program that could generate distinct puzzles in a snap.