How to Play Sudoku

What is Sudoku?

Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9x9 grid with digits so that each column, each row, and each of the nine 3x3 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.

The Basic Rules

• Rule 1: Each Row Must Contain All Digits 1-9
  Look at any horizontal line across the grid. Every number from 1 to 9 must appear exactly once in that row. No duplicates allowed!
• Rule 2: Each Column Must Contain All Digits 1-9
  Similarly, for any vertical line down the grid, every number from 1 to 9 must appear exactly once. Again, no duplicates.
• Rule 3: Each 3x3 Box Must Contain All Digits 1-9
  The 9x9 grid is divided into nine smaller 3x3 boxes. Within each of these boxes, every number from 1 to 9 must appear exactly once.
• Rule 4: Only Use Digits 1-9
  You can only use the numbers 1, 2, 3, 4, 5, 6, 7, 8, and 9. No zeros, no tens, etc.
• Rule 5: Don't Change Given Numbers
  The numbers initially provided in the grid are fixed. You cannot change or remove them. They are your starting clues!