Peak Puzzle

Sudoku

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Player’s guide

The classic logic puzzle: fill the 9×9 grid so that every row, every column and every 3×3 box contains the digits 1–9 exactly once. No guessing is ever needed — a proper sudoku always has one solution you can reason your way to. Standard and Advanced boards arrive daily at midnight UTC, each with its own clock and daily best.

  1. 1

    Read the board

    Printed digits are the givens — they never move. Your own entries appear in blue, and a wrong digit turns red the moment you place it. Mistakes cost time, not lives, so an experiment is never fatal.
  2. 2

    Select and fill

    Click a cell and type a digit. To work faster, drag across several cells — or Shift/Ctrl-click to build up a selection — and one keystroke fills them all. Handy when a digit’s remaining homes are all decided at once. Entering the same digit again clears the cell, which is how you take a placement back on a phone.
  3. 3

    Pencil in candidates

    Switch to Candidates mode (or hold the thought and press C) to jot candidate digits into empty cells, just like pencil marks on paper. Place a digit and it sweeps itself out of the candidates in its row, column and box.
  4. 4

    Or let Auto do the pencilling

    Turn on Auto candidates(A) and every empty cell shows the digits its row, column and box haven’t ruled out — recomputed after each placement, so the marks are never stale. The real work still happens in Candidates mode: strike a digit out and it stays struck, because your strikes are kept apart from the computed set. Erase a cell to hand it back its full set, and take a wrong entry back and the candidates it was hiding return — minus the ones you had already ruled out. Your hand-written marks wait untouched behind the auto view and come back the moment you switch it off.
  5. 5

    Keep your hands on the keys

    The whole board plays from the keyboard:
    ← ↑ ↓ →move between cells
    1–9enter a digit
    Backspaceerase
    Ctoggle Candidates mode
    Atoggle Auto candidates
    CtrlZundo
    Ctrl⇧Zredo
Tip: Open every board the same way: scan each digit 1 through 9 and ask where it must go in each box. Those forced placements cascade — and when they dry up, good candidates are what break the logjam.