A Sudoku puzzle is defined as a logic-based, number-placement puzzle. Players insert the numbers one to nine into a grid consisting of nine squares subdivided into a further nine smaller squares in such a way that every number appears once in each horizontal line, vertical line, and square.
The objective is to fill a 9×9 grid with digits in such a way that each column, each row, and each of the nine 3×3 grids that make up the larger 9×9 grid contains all of the digits from 1 to 9. Each Sudoku puzzle begins with some cells filled in. The player uses these initial numbers as a starting point towards discovering the unique solution. It is important to make sure that no number from 1 to 9 can be repeated in any row or column (although, the can be repeated along the diagonals)