How to play Sudoku
Fill the grid so every row, every column and every three-by-three box holds the digits 1 to 9 once each. Three boards a day — Easy, Medium and Hard — and none of them ever needs a guess. On the second shelf, outside the daily line-up.
Play today's Sudoku · Watch the gameplay demo
The rules
- Tap a cell, then a digit on the nine-key pad. Each key counts how many of its digit are still to place, and dims when all nine are in. The selected cell tints its row, column and box and lights its digit everywhere on the board.
- Every entry is checked at once. The right digit locks in. A digit already in the cell’s row, column or box is refused, free — the cell that clashes is ringed, and nothing is charged.
- A digit the board allows but the puzzle does not is a mistake: it shows red until you replace it, costs 8 points, and its key is struck for that cell. The same wrong digit tried there again is refused, free.
- Notes pencils candidates into a cell: switch it on, tap the digits a cell could be, switch it off. Notes are never checked and never cost, and a digit you place takes itself out of the notes in its row, column and box. Erase clears a wrong digit or a cell’s notes.
- Hint fills the next cell a solver would — and says why, under the board. When a pattern has to clear candidates first, the pattern is named and ringed. A hint costs 4 points and asks twice before it spends them.
- Three boards, one score. Easy, Medium and Hard are three different puzzles, each keeping its own progress, so you can switch between them freely. The first board you finish is the day’s score. The other two stay open to play for fun and change nothing.
- Your progress is saved move by move, so a refresh is not a second attempt; the archive holds every past day.
The three levels
A level is not a guess at how hard a board feels: it is the hardest technique the board forces, worked out by a solver that only makes moves a person could explain.
- Easy — 36 or 37 digits given, and every cell falls to scanning: a digit with only one place left in a row, a column or a box.
- Medium — 28 to 34 given. Somewhere the singles run dry and you need a locked line (a digit confined to one row or column inside a box) or a bare pair (two cells that hold the same two candidates).
- Hard — 24 to 32 given. It needs a pattern that wants the candidates penciled in: a hidden pair, a triple, an X-wing or an XY-wing.
Because every board is dug only as far as that solver can still finish it, no board ever needs a guess — and each has exactly one solution.
Strategy
- Scan before you pencil. Pick a digit and ask where it can go in each box. A box with one open place for it is a cell solved. Easy boards fall to this alone.
- Work the crowded places. A row, column or box with two or three empty cells is nearly decided; so is a digit with seven or eight already placed — the keys show the count.
- Let the clash rule check your scan, not replace it. A refused digit is free, but the first digit the board allows is a real try. A blind pick between two candidates costs 4 on average — exactly a hint’s price — so guessing never beats asking.
- On Medium and Hard, pencil the stuck region. When a digit in a box can only sit in one row, it leaves the rest of that row. When two cells in a unit hold the same two notes, no other cell there can hold either.
- Read the hint’s reason. It names the technique that opened the cell. The next time the board stalls, look for that shape first.
Scoring
A board finished clean is 100. Each wrong digit costs 8 and each hint 4, down to a floor of 10; a board whose every empty cell was filled by a hint is not a solve, and scores 0. A clash, a note and an erase are free, and the clock is shown on the results sheet but never scored. So one mistake and one hint is 88. The three levels score on the same curve, and only the first board you finish counts. Sudoku sits outside the daily line-up, so its score never moves your day’s total.
Full details on how scoring works.