How to play Ninefold Sudoku
Sudoku basics
Fill each row, column, and 3×3 box with the digits 1 through 9 without repeating a digit.
Selecting cells and entering values
Select an editable cell, then choose a digit. Clues are fixed. Direct conflicts are marked with text and a symbol as well as color. Erase removes an entered value.
Notes
Turn on Notes before entering digits to record candidates. In Co-op, notes are shared. When automatic note removal is enabled, an accepted value removes that digit from related cells.
Guided and Classic Solo
Guided marks solution-wrong entries immediately and provides Check Board. Classic shows only direct Sudoku conflicts until the board is submitted for completion. Both styles support notes, pause, Nudge, and Reveal.
Co-op rooms
Create a private room, share its six-character code, ready up, and solve one board together. The server decides which simultaneous move is accepted.
Error presets
Casual accepts entries and may show correctness. Challenge rejects solution-wrong entries and adds a five-second result penalty. Blind hides solution correctness. Clean accepts only solution-correct entries. Direct row, column, and box conflicts remain visible.
Hints
Nudge points toward a deterministic next step without entering a value. Reveal enters one eligible value. Solo hints add 20 seconds to the result. Explain hints are not part of this release.
Keyboard controls
Use arrow keys to move, digits to enter values, Backspace or Delete to erase, and N or Space to toggle notes, H for a Nudge where hints are available, and Escape to clear selection.
Replay
Completed multiplayer matches can be played, paused, stepped, and scrubbed. Integrity is shown as verified only after the browser checks the event chain and server signature. Solo replays stay on the device.
Accessible play
Every cell announces its row, column, clue or editable state, value, notes, conflict, and multiplayer attribution when present. Status is never communicated by color alone.
Reconnect
If your connection drops, confirmed state is preserved. Input pauses until the room is synchronized again.