How to Play Sudoku - Game Guide
Welcome to our online Sudoku game! This comprehensive guide will walk you through all the features and controls, helping you make the most of every function for a smooth and enjoyable gaming experience.
1. Starting a Game
Choose Difficulty Level
The game offers 5 difficulty levels, from beginner to master:
- Beginner (0-1 stars) - Perfect for newcomers with more hints
- Intermediate (1-2 stars) - Slightly challenging, requires basic techniques
- Advanced (2-3 stars) - Requires intermediate solving strategies
- Expert (3-4 stars) - Demands advanced techniques and logical reasoning
- Master (4-5 stars) - Extremely challenging, requires expert-level skills
Auto-Save Recovery
When you return to the game, the system automatically restores your last unfinished game. You can also manage all saved games in the "Unfinished Games" list on the launch panel.
2. Four Input Modes
The game provides 4 different input modes that you can switch between at any time:
📝 Big Number Mode
Default mode. Fill in definite answer digits (1-9) in cells. This is your final answer that you believe is correct.
🔢 Corner Mode
Mark candidate numbers in the four corners of cells. Used to track possible digits for later elimination and analysis.
⊙ Center Mark Mode
Mark candidate numbers in the center of cells. Similar to corner marks but displayed centrally, suitable for simplified candidate notation.
🎨 Color Mark Mode
Add color labels to cells (up to 9 colors). Used for advanced techniques like coloring, chain reasoning, helping visualize relationships.
How to switch: Click the mode buttons on the tool panel to switch. The currently active mode will be highlighted.
3. Smart Cell Selection
Single Click Selection
Click any cell to select it. Supports both mouse and touch operations. Selected cells will be highlighted.
Double-Click/Long-Press Batch Selection ⭐
This is a unique feature! Double-click (click twice within 300ms) or long-press (hold for 800ms) a cell, and the system will intelligently select related cells in batch:
- Color Labels - If the cell has a color, select all cells with the same color
- Same Big Number - If the cell has a number (e.g., "5"), select all cells with "5"
- Same Corner Marks - If the cell has corner candidates, select all cells containing these candidates
- Same Center Marks - If the cell has center marks, select all cells with the same marks
Practical Application: In advanced solving techniques (like X-Wing, chain reasoning), quickly selecting all cells with the same number or color can dramatically improve analysis efficiency!
4. Three Input Methods
Touch/Mouse
Click digit buttons (0-9) on the tool panel
Keyboard Shortcuts
Press digit keys 0-9 directly for quick input (0 to delete)
Mobile Optimized
Perfect touchscreen support with responsive layout
5. Smart Delete Function
Delete operations follow a priority hierarchy to avoid clearing all marks at once:
Delete Order in Color Mode
Color → Big Number → Center Marks → Corner Marks
Delete Order in Other Modes
Big Number → Center Marks → Corner Marks → Color
Shortcuts: Press Delete or Backspace to delete, or click the "0" button on the tool panel.
6. Auto-Save System
The game automatically saves your progress in these situations:
- After each number entry or deletion
- When switching to another browser tab
- Before closing the browser window
Save List Management
In the "Unfinished Games" section of the launch panel, you can:
- View all saves - Shows game progress percentage and difficulty
- Sort saves - Supports 5 sorting methods (recently updated, progress, difficulty, etc.)
- Resume game - Click any save to continue playing
- Delete saves - Delete individual saves or clear all at once
7. Undo & Redo
The game supports complete operation history:
- Undo Operation - Click the undo button to go back one step
- Redo Operation - Click the redo button to go forward one step
- Efficient Storage - Based on diff algorithm, only records changes
8. Answer Check
Click the "Check" button and the system will intelligently analyze your answer:
✅ All Correct
Congratulations popup appears, asking if you want to start a new game
❌ Has Errors
Error cells show conflict markers, counts number of mistakes
⏳ Partially Correct
Shows number of filled cells and remaining empty cells
9. Pause & Resume
Need to step away? Click the timer area or pause button:
- The board shows a blur overlay to protect your progress
- Timer stops counting
- Click "Resume Game" button to continue
10. Replay Options
The game provides two replay methods:
⏱️ Replay with Time
Clears all filled content but keeps the elapsed time. Perfect for challenging yourself to improve on the same puzzle.
🔄 Reset Time Replay
Clears all content and resets timer to 0. Completely start over as if playing the puzzle for the first time.
11. Responsive Layout
The game automatically adjusts layout based on your device and screen orientation:
🖥️ Landscape Layout (Widescreen)
When width ≥ height×1.2, Sudoku occupies 67% width, tool panel on the right
📱 Portrait Layout (Vertical)
In other cases, Sudoku occupies 72.5% height, tool panel at the bottom
12. Mobile Optimization
On small screen devices, the game provides additional mobile features:
- Hamburger Menu - Contains "Start Game" and "Help" functions
- Touch Optimized - Perfect touchscreen support
- Auto-Close - Menu automatically closes when clicking outside or scrolling
💡 Tips Summary
- Use all four input modes - Big numbers for answers, corner/center marks for candidates, color marks for advanced techniques
- Master double-click/long-press - Quickly batch-select same elements, dramatically improve analysis efficiency
- Use keyboard shortcuts - Pressing digit keys is faster than clicking with mouse
- Check answers regularly - Catch errors early to avoid wasting time
- Use undo function - Don't fear mistakes, boldly try different solving approaches
- Manage saves - Play multiple difficulty games simultaneously, switch anytime