How to play Sudoku

Sudoku is a logic puzzle with one rule at heart: every row, column and box must contain the numbers 1 to 9 exactly once. No maths is needed, only careful reasoning.

The grid

A Sudoku board has 81 squares in a 9×9 grid. Thicker lines divide it into nine boxes, each 3×3. Some squares start with a number (the “givens”). Your job is to fill in the rest.

The three rules

• Rows: each of the nine horizontal rows contains 1 to 9, with no repeats.
• Columns: each of the nine vertical columns contains 1 to 9, with no repeats.
• Boxes: each of the nine 3×3 boxes contains 1 to 9, with no repeats.

Every puzzle on Hue Sudoku has exactly one correct solution, so you never need to guess.

Playing on Hue Sudoku

• Tap a square to select it, then tap a number from the row at the bottom. On a computer you can type 1 to 9 instead.
• Each digit has its own colour. Select a number and every matching square lights up, which makes patterns easy to spot.
• The number row shows how many of each digit are left to place.
• Notes lets you pencil in small candidate numbers. They clear automatically when you place a digit in the same row, column or box.
• Undo steps back a move, Erase clears a square, and Hint fills one square for you (it adds 30 seconds to your time).
• Wrong numbers turn red and add to your mistake count.

Choosing a difficulty

Easy puzzles give you more starting numbers and can be solved with simple scanning. Medium, Hard and Expert give you fewer, and need more advanced techniques. Start on Easy, and move up when you finish a puzzle without mistakes. See our solving strategies for the techniques behind each level.