RULES

Sudoku is a popular puzzle game played on a grid of 9x9 cells. The rules are simple:

1. The grid consists of 9 rows, 9 columns, and 9 3x3 subgrids.
   
2. The objective is to fill the grid with digits from 1 to 9, making sure that each row, each column, and each 3x3 subgrid contains all of the digits from 1 to 9 without repetition.
   
3. Initially, some of the cells in the grid are filled with digits. These are known as "clues" or "givens."
   
4. To solve the puzzle, you need to use logic and deduction to fill in the remaining empty cells while adhering to the rules mentioned above.
   
5. The puzzle is considered solved when all cells are filled correctly, meeting the criteria of no repetition in rows, columns, and subgrids.
   

In summary, the challenge of Sudoku lies in logical deduction and pattern recognition to systematically fill in the grid, ensuring that every row, column, and subgrid contains each digit exactly once.