Rules- Each row must contain digits 1–9 exactly once.
- Each column must contain digits 1–9 exactly once.
- Each 3×3 box must contain digits 1–9 exactly once.
- The puzzle starts with some given digits (clues). You fill in the rest.
- Every puzzle has exactly one unique solution.
Game Controls- Erase — Remove the value from the selected cell.
- Clear — Reset all user entries back to the starting puzzle.
- Notes — Toggle pencil-mark mode to jot down candidate digits.
- Center — Toggle center-mark mode to highlight confirmed digit subsets.
- Auto-fill — Fill candidate notes for all empty cells at once.
- Hint — Reveal the next logical step with highlighted cells.
Conflict Detection- Conflicts — Highlights cells with duplicate digits in the same row, column, or box.
- Wrong — Highlights cells that don't match the solution.
- Off — No conflict highlights.
Keyboard Shortcuts- 1–9 — Enter a value depending on active mode (Value / Notes / Center).
- Shift+1–9 — Force toggle a pencil mark on all selected cells.
- Ctrl/Cmd+1–9 — Force toggle a center mark on all selected cells.
- 0 / Delete / Backspace — Erase selected cell(s).
- Arrow keys / WASD — Navigate the grid. Hold Shift to extend the selection.
- Double-tap a digit — Stamp that number on subsequent cell clicks.
- Long-press a cell — Erase its value (300ms).
- Ctrl+Z / Ctrl+Y — Undo / Redo.
- Ctrl/Cmd+A — Select all non-given cells.
- H — Get a hint.
- Escape — Clear selection and dismiss hints.
Submit- Submit — Submit the completed grid for validation. All cells must be filled.
Multi-Select- Ctrl/Cmd+click — Toggle a cell into the multi-selection set.
- Shift+arrow — Extend selection as you move.
- Color, pencil marks, erase, and erase-color all apply to every selected cell.
- Value placement and number stamp affect only the primary (last-clicked) cell.
Color Marker: Select a color from the picker, then tap a cell to mark it. Tap the same color again to remove it. Works on multiple selected cells.