How to play Sudoku
- Press Start. The printed numbers are clues and cannot be changed.
- Tap an empty cell to select it. Its row, column and 3 x 3 box light up.
- Tap a number on the pad (or type it) to write it in. A wrong number flashes red and counts as a mistake; three mistakes end the round.
- Turn on Notes to pencil in small candidate numbers. Writing a number clears that number from the notes around it.
- Fill every cell to solve the puzzle. No mistakes and no hints earns three stars.
About Sudoku
This is classic Sudoku with the feel of a good notebook. The grid has nine rows, nine columns and nine 3 x 3 boxes, and a few numbers are already printed in. Your task is to fill every empty cell so that each row, each column and each box contains the numbers 1 to 9 exactly once. Tap a cell, tap a number, and it is written in ink. Switch on notes to pencil in small candidates, undo any step, and erase what you no longer need. The selected cell lights up its row, column and box, every copy of the same number is highlighted, and finished rows, columns and boxes glow as they complete. Every puzzle has exactly one solution, and each one is graded by the hardest technique a logic solver needs to finish it: Gentle puzzles fall to simple scanning, while Master puzzles call for pairs, triples and the occasional X-wing. When you are stuck, the hint does not just fill a cell; it tells you why that number has to go there. A new daily puzzle arrives every midnight.
Controls
| Input | What it does |
|---|---|
| Tap a cell | Select it |
| Number pad or 1 to 9 | Write a number |
| Arrow keys | Move the selection |
| N or Notes | Switch pencil notes on or off |
| Backspace or Erase | Clear the cell |
| U or Undo | Take back the last step |
| H or Hint | Show the next logical step (costs a star) |
Tips and strategy
- Scan one number at a time. Pick a digit that already appears often, say 7, and check each box that is missing it: the rows and columns with a 7 rule out most cells quickly.
- Look for the last empty cell in a row, column or box. With eight numbers in place, the ninth fills itself.
- Use notes from the Steady chapter on. Pencilling in every candidate for a few crowded cells turns guesswork into elimination.
- Watch for pairs. Two cells in a row that can only hold the same two numbers claim them, so no other cell in that row can use either.
- Use pointing pairs. If a number's only places in a box all sit in one row, that number cannot appear anywhere else in that row outside the box.
- If you are truly stuck, take a hint and read the reason. Each hint names the technique it used, which is the quickest way to learn the harder ones.
Questions and answers
Does every puzzle have only one solution?
Yes. Every grid is checked by a solver that counts solutions, and any grid with more than one is thrown away. The clues are also placed in a symmetrical pattern, like a hand-made puzzle.
How is difficulty decided?
By technique, not just by the number of clues. A logic solver works through each puzzle and records the hardest step it needed: single candidates for Gentle, hidden singles for Steady, pointing pairs for Tricky, pairs and triples for Expert, and up to X-wings for Master.
What happens when I make a mistake?
A wrong number flashes red, is not written in, and counts as a mistake. After three mistakes the round ends and you can try the same puzzle again.
How do stars work?
Solve with no mistakes and no hints for three stars. Each mistake or hint takes away one star, and a solved puzzle always earns at least one.
Is there a daily Sudoku?
Yes. A new Tricky-level puzzle arrives every midnight, the same for every player, so you can compare times.
Do I need an account?
No. Sudoku runs in your browser on phones, tablets and computers, and your stars are saved on your device.
