📖 What is Sudoku?
Sudoku is a logic-based puzzle game from Japan. The goal is to fill a 9×9 grid with digits 1 through 9.
🎯 Golden Rule: Each digit from 1 to 9 must appear exactly once per row, column, and 3×3 box.
Sudoku helps improve logic, memory, and concentration. It's a perfect brain training activity!
📜 The 3 Essential Rules
📏 Rule 1: Rows
Each horizontal row must contain all digits from 1 to 9, with no repetition.
📐 Rule 2: Columns
Each vertical column must contain all digits from 1 to 9, with no repetition.
⬛ Rule 3: 3×3 Boxes
Each 3×3 box must contain all digits from 1 to 9, with no repetition.
⚠️ Important: A single cell can only contain one digit! Notes (pencil mode) are for tracking your hypotheses.
🎓 Beginner Tips
💡 Tip 1: Start with obvious cells
Look for rows, columns, or boxes missing only one digit. That's the easiest way to start!
💡 Tip 2: Use "Pencil Mode"
Before making a decision, note all possible digits in a cell. This helps you visualize possibilities.
💡 Tip 3: Single Candidate Technique
If a cell has only one possible digit in its row/column/box, that's the correct one!
💡 Tip 4: Check regularly
Click "Check" to see if you've made any mistakes. Better to correct early!
🚀 Advanced Strategies
Once you master the basics, try these advanced techniques:
🔍 Hidden Pairs
🔍 Naked Triples
🔍 X-Wing
🔍 Swordfish
🔍 Coloring
🔍 XY-Chain
🔍 Forcing Chains
🔍 Unique Rectangle
These techniques are essential for Hard and Master levels!
⭐ Difficulty Levels
- 🍃 Easy (41 digits) - Perfect for beginners
- 🌙 Medium (26 digits) - Requires more thinking
- 🔥 Hard (16 digits) - For experienced players
- 👑 Master (9-10 digits) - Extreme challenge!
The more empty cells, the harder the puzzle. Master level has only ~10 clues!
🎮 Game Interface
- ⏱️ Timer: Track your solving time
- ❌ Errors: Counts incorrect moves
- ✏️ Pencil Mode: Take notes in cells
- 🎲 New Game: Start a fresh puzzle
- ✓ Check: Verify your solution
- 💡 Hint: Get help for selected cell
- ⚡ Solution: See complete solution
🎨 Color Code Guide
Highlighted cells belong to the same row, column, or 3×3 box as your selection.
⚠️ Common Mistakes
❌ Don't ignore errors!
When you see red, correct it immediately. One error can lead to many!
❌ Don't guess randomly!
Sudoku is about logic, not luck. Always have a reason for placing a number.
❌ Don't stay stuck!
If stuck on one cell, move to another. Sometimes taking a break helps!
📚 Glossary
- Clue / Given: Initial digit that cannot be changed
- Pencil Mode: Allows you to note temporary digits in a cell
- Grid: The complete set of 81 cells
- Box / Block: A 3×3 square of cells
- Candidate: Possible digit for a cell
- Backtracking: Method of trial and error
- Naked Pair: Two cells with the same two candidates
- Hidden Pair: Two candidates that appear only in two cells of a unit
❓ Frequently Asked Questions
🔹 Is Sudoku good for your brain?
Yes! Sudoku improves logic, memory, concentration, and can help prevent cognitive decline.
🔹 How long does it take to solve a Sudoku?
Easy puzzles: 5-15 minutes. Hard puzzles: 20-60 minutes. Master puzzles: hours!
🔹 Can I play offline?
All games are saved in your browser. Once loaded, you can play offline!
🔹 How many puzzles are there?
200 unique puzzles: 50 Easy, 50 Medium, 50 Hard, 50 Master!
🔹 What does Pencil Mode do?
Pencil Mode lets you write small notes in cells to remember possible digits.
📈 Tips to Improve
✅ Daily Practice: Play at least one puzzle per day to improve.
✅ Time Yourself: Try to beat your personal best times.
✅ Learn One Technique at a Time: Master basic techniques before advanced ones.
✅ Play Higher Difficulties: Challenge yourself with Hard and Master levels.
💡 Did You Know?
- The first Sudoku puzzle was published in 1979 in New York!
- "Sudoku" means "single number" in Japanese.
- There are 6,670,903,752,021,072,936,960 possible Sudoku grids!
- World champion solves Sudoku in under 3 minutes!
- Sudoku requires no math skills - only logic!