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Sudoku

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    Overview

    Sudoku is a logic puzzle on a 9 by 9 grid split into nine 3 by 3 boxes. Some squares start with a digit; fill the rest so that each row, each column and each box holds every digit from 1 to 9 once. No arithmetic is involved, only placement.

    Each puzzle here is made fresh when you start and kept only if it can be finished by reasoning alone, so it has a single solution and never needs a guess. Easy and Medium need nothing beyond spotting the one place left for a digit; Hard adds pairs and pointing digits; Expert needs triples, X-wings, swordfish or XY-wings somewhere along the way. Each difficulty has its own scoreboard.

    Made by
    wasmga.me
    Released
    2026

    Controls guide

    On the board

    KeyAction
    Click/touchPick a square; drag to move the pick
    Arrow keysMove between squares
    1to9Write a digit, or a note while notes are on; the same digit again takes it out
    Shift+1to9The other kind: a note while notes are off, a digit while they are on
    Backspace/Delete/0Erase the square
    NNotes on or off
    UUndo
    HHint
    Enter/PPause

    Buttons

    KeyAction
    1to9Write that digit in the picked square; the small number under it counts how many are still to place
    UndoTakes back the last change, notes it cleared included
    EraseClears the picked square
    NotesWhile lit, digits go in as small notes
    HintTakes out a wrong digit if there is one, otherwise writes the next digit reasoning finds and says why

    Controller

    KeyAction
    D-padMove between squares
    ARun the square through 1 to 9
    BErase
    StartPause

    Cheatsheet

    Difficulty

    Easy
    About 38 clues, single digits only
    Medium
    About 30 clues, single digits only
    Hard
    Pointing digits, box and line, naked and hidden pairs
    Expert
    Triples, X-wing, swordfish, XY-wing

    On the grid

    Shaded squares
    The row, column and box of the picked square
    Darker squares
    The same digit as the picked square
    Red digit
    The same digit twice in a row, column or box
    Notes
    Clear themselves from a row, column and box when a digit goes in
    Flash
    A row, column or box just filled with no repeats

    Score

    Points
    200000 times the difficulty (1 to 4), divided by the seconds taken plus 120
    Hints
    Each one counts as a minute more

    Tips

    1. Start with the digits already on the board most often: with seven or eight of one digit placed, the last ones usually have a single box left to go in.
    2. Scan one box at a time and ask, for each missing digit, which of its empty squares are not ruled out by the rows and columns crossing it. One square left means the digit goes there.
    3. When a square looks hard, count what its row, column and box already hold. If eight different digits are there between them, the ninth is the answer.
    4. On Hard and Expert, write notes. If a digit's notes in a box all sit in one row, that digit can't go anywhere else along that row, and the notes it clears often open a single.
    5. Two squares in a unit that can only hold the same two digits share them between them, so those two digits come out of every other square of that unit.
    6. A hint first looks for a wrong digit. If one is taken out, everything worked out from it is worth a second look.