Sudoku

Sudoku (数独 sūdoku, digit-single) (/suːˈdoʊkuː/ (About this sound listen), /-ˈdɒ-/, /sə-/, originally called Number Place is a logic-based, combinatorial number-placement puzzle, and a free game without need to internet.
The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 subgrids that compose the grid (also called "boxes", "blocks", or "regions") contains all of the digits from 1 to 9.
The puzzle setter provides a partially completed grid, which for a well-posed puzzle has a single solution.