Sudoku

Sudoku (数独 sūdoku) is a logic-based 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") 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. • Easy, Normal, Hard, Extreme Sudokus. • CELL FIRST or NUMBER FIRTS playing strategies • Unlimited time, unlimited hints.