Sudoku++ — User Guide
What is Sudoku?
Sudoku is a logic-based number puzzle. The goal is to fill a grid so that every row, every column, and every box (the smaller sub-grids) contains each number exactly once. For a 9×9 puzzle, that means each row, column, and 3×3 box must contain the numbers 1 through 9 with no repeats. Smaller grids (4×4, 6×6) follow the same rule with fewer numbers.
No maths or arithmetic is involved — it's pure logical deduction. Each puzzle starts with some cells pre-filled (the given numbers), and you use the clues to work out the rest. Every puzzle generated by Sudoku++ has exactly one unique solution.
Quick Start
- Open /puzzles/sudoku.
- Choose a Grid size (4×4, 6×6, or 9×9).
- Choose a Difficulty (Easy, Medium, Hard).
- Click New Game.
- Click a cell to select it, then enter a number using the number pad or keyboard.
- Fill all cells correctly to complete the puzzle.
Controls
| Control | What it does |
|---|---|
| Grid | Select puzzle size — 4×4 (quick), 6×6 (casual), 9×9 (standard). |
| Difficulty | Easy (fewer empty cells) to Hard (more empty cells, harder to deduce). |
| New Game | Generates a fresh puzzle with the selected size and difficulty. |
| Notes | Toggle pencil-mark mode. In this mode, tapping a number toggles a candidate note in the cell. |
| Undo | Reverts your last move (up to 50 moves). |
Number Pad
The number pad below the grid shows buttons for each number (1–N) plus a clear button (✕). Click a number to enter it in the selected cell. Click the same number again to clear it. Click ✕ to clear the cell.
Keyboard Shortcuts
| Key | Action |
|---|---|
| 1–9 | Enter number |
| Backspace / Delete | Clear cell |
| Arrow keys | Move selection |
| Ctrl+Z / Cmd+Z | Undo |
Tips
- Use Notes mode to track candidate numbers in cells. This is especially helpful for harder puzzles.
- Start with the grid size that suits you — 4×4 is great for learning the mechanics, 9×9 for a real challenge.
- Keyboard shortcuts make the game much faster: number keys to enter, arrows to navigate.
- Click a cell with a number to see all other cells with the same number highlighted — useful for spotting patterns.
- Pencil marks auto-clear when you enter a final number in a cell.
What's new in Sudoku++
- Three grid sizes (4×4, 6×6, 9×9) for all skill levels
- Three difficulty levels with unique-solution verification
- Pencil marks for note-taking
- Undo support (up to 50 moves)
- Keyboard shortcuts for fast play
- Touch-friendly number pad
- Theme-aware colours matching your Bootswatch selection