How to Play Sudoku puzzlesecret.com/how-to-play-sudoku
The one rule: every row, every column and every 3×3 box must contain the digits 1 to 9 exactly once. No maths. No guessing. Use a pencil.
Question one: where can this number go?
- Pick a box that is nearly full, and a number it is missing.
- Find that number elsewhere on the grid. It rules out its whole row and its whole column.
- Cross off those squares in your box. One empty square left? Write the number in.
- Two squares left? Leave it. Try another number.
Question two: what can go in this square?
- Look at one empty square. Tick off every number in its row, its column and its box.
- Only one number left? Write it in.
- Easiest case: a row, column or box with eight numbers. The ninth goes in the gap.
Stuck? Try these in order
- Any row, column or box with one or two gaps.
- The number that appears most on the grid: where can it go in each box?
- Switch shape: from boxes to rows, or to columns.
- Recheck around the last number you placed.
- Harder puzzle? Pencil tiny notes in squares with only two options, then go round again.
Made a mistake?
Find the number that appears twice in one row, column or box. Erase back to the last number you were sure of. Check just that box against the answers.
Always look three ways
Row, column and box. Forgetting the box is the most common slip.
From Sudoku with a Secret, Volume 1 by Dan Herlehy: 200 puzzles, 70 easy ones first, one big grid per page, answers in the back. Paperback on Amazon, or see puzzlesecret.com.