How to play Sudoku
Sudoku on this site is the classic 9×9: digits 1 through 9 in every row, column, and 3×3 box. The givens stay put. There is only one way to finish the grid. A puzzle is solved when every cell is filled and no row, column, or box repeats a digit.
The full how-to — rules, how to play, and beginner strategy — is here: How to play Sudoku. Or Play Sudoku.