How to play Sudoku

Fill every empty square. A finished puzzle has each digit from 1 through 9 in every row, every column, and every 3 by 3 box.

The printed numbers, called givens, are fixed. The empty squares are where your logic goes.

A row runs left to right. A column runs top to bottom. A box is one of the nine 3 by 3 areas marked by heavier borders.

Before you place a digit, check all three. If a 7 is already in the same row, column, or box, that square cannot be 7.

Notes are small candidate marks for digits that might fit in an empty square. They are not guesses; they are reminders.

Keep notes limited to real possibilities. When you place a number, remove that number from notes in the same row, column, and box.

Look for rows, columns, or boxes that already contain many digits. A nearly full area usually has fewer possibilities to check.

Place a number only when it is forced. If you are unsure, add a note and move to another part of the grid.

Do not place a digit just because it feels likely. A well-formed Sudoku can be solved without guessing.

Do not let notes pile up without review. After every confirmed number, re-scan the affected row, column, and box.