Zudoku

Sudoku, sometimes written Su Doku, is a logic-based placement puzzle, also known as Number Place in the United States. The aim of the puzzle is to enter a numerical digit from 1 to 9 in each cell of a 9x9 grid, starting with various digits given in some cells (the "givens"). The grid is made up of 3x3 subgrids (called "regions"). Each row, column, and region must contain only one instance of each numeral. Completing the puzzle requires patience and logical ability. Although first published in 1979, Sudoku initially caught on in Japan in 1986 and attained international popularity in 2005.