Sudoku

🕹️How to Play

1. 1The 9×9 grid is partially filled with digits 1–9.
2. 2Select any empty cell and tap a number from the number pad to fill it.
3. 3Enable pencil mode to write small candidate notes inside a cell.
4. 4Use the Hint button to reveal the correct answer for one empty cell.
5. 5Press Undo (↩) to revert your last move at any time.
6. 6Three mistakes end the game — double-check before placing.

📋Rules

• ▸Every row must contain each digit 1–9 exactly once.
• ▸Every column must contain each digit 1–9 exactly once.
• ▸Every 3×3 box must contain each digit 1–9 exactly once.
• ▸Pre-filled clue cells cannot be changed.
• ▸Making 3 incorrect placements ends the game immediately.
• ▸Hints are unlimited but each one reduces your final score.

💡Pro Tips

• ★Start with rows, columns, or boxes that already have 7 or 8 filled digits.
• ★When a digit can go in only one cell within a box, it must go there — this is called a "hidden single".
• ★Pencil mode is your best friend on Hard and Expert — annotate before committing.
• ★Eliminate candidates systematically: when you place a number, clear it from all notes in the same row, column, and box.
• ★On Expert mode, look for "naked pairs" — two cells in the same unit that share exactly two candidates.

ℹ️About

Sudoku is one of the world's most popular logic puzzles, originally published in Japan in the 1980s under the name "Number Place." This browser version offers four difficulty levels — Easy (38–45 clues), Medium (30–37), Hard (25–29), and Expert (22–24 with guaranteed unique solution) — so beginners and seasoned solvers alike can find the perfect challenge. The scoring system rewards speed and accuracy: start from 10,000 points and subtract time penalties, mistake penalties (−500 each), and hint penalties (−300 each), then multiply by a difficulty factor up to ×4 for Expert. Pencil mode lets you annotate candidates without committing, the undo stack preserves your full move history, and the game auto-saves your best score per difficulty to browser storage. Statistics track your personal bests so you can always push for a new record.