How to Play Sudoku

1. 1. The Grid

   Sudoku is played on a 9×9 grid, divided into nine 3×3 boxes. Some cells contain given numbers (clues).

2. 2. Row Rule

   Each row must contain the digits 1-9 exactly once. No digit can repeat in a row.

3. 3. Column Rule

   Each column must contain the digits 1-9 exactly once. No digit can repeat in a column.

4. 4. Box Rule

   Each 3×3 box must contain the digits 1-9 exactly once. No digit can repeat within a box.

5. 5. Unique Solution

   Every valid Sudoku puzzle has exactly one solution. Use logic, not guessing!

┌───────┬───────┬───────┐
│ 5 3 · │ · 7 · │ · · · │
│ 6 · · │ 1 9 5 │ · · · │
│ · 9 8 │ · · · │ · 6 · │
├───────┼───────┼───────┤
│ 8 · · │ · 6 · │ · · 3 │
│ 4 · · │ 8 · 3 │ · · 1 │
│ 7 · · │ · 2 · │ · · 6 │
├───────┼───────┼───────┤
│ · 6 · │ · · · │ 2 8 · │
│ · · · │ 4 1 9 │ · · 5 │
│ · · · │ · 8 · │ · 7 9 │
└───────┴───────┴───────┘

Given numbers are fixed.
Fill empty cells (·) with 1-9.

• Scan for singles — Look for rows, columns, or boxes missing just one digit.
• Use pencil marks — Note possible candidates in empty cells to track options.
• Look for naked pairs — Two cells with the same two candidates can eliminate those from other cells.
• Check intersections — Where a row/column intersects a box, one may constrain the other.
• Work systematically — Focus on one digit at a time, finding all its placements.
• Never guess — Every Sudoku has a logical solution. If stuck, look for patterns.