Sudoku

Sudoku is a logic-based, combinatorial number-placement puzzle. 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") contain all of the digits from 1 to 9. The puzzle setter provides a partially completed grid, which typically has a unique solution. Sudoku puzzles vary in difficulty, ranging from simple and straightforward to extremely challenging. The simplicity of the rules combined with the complexity of the logic needed to solve the puzzle makes Sudoku popular and engaging for players of all ages.