Happy Sudoku is an intelligent Sudoku game developed with Flutter, combining AI technology with innovative level design. The game features a dynamic infinite-scrolling level selection system, providing players with a unique gaming experience.

#### Core Features

1. **Innovative Level System**
* **Dynamic Level Path**: Programmatically generated infinite scrolling curve path for level display
* **Stage-based Layout**: Levels divided into multiple stages, each containing a fixed number of levels
* **Smart Loading**: Lazy loading technology for optimized performance and memory usage
* **Smooth Experience**: Intelligent scroll monitoring and preloading mechanism
* **Visual Feedback**: Current level highlighting, clear stage separation, and special character display

2. **Smart Game Features**
* **AI Hint System**: Intelligent analysis of solving strategies
* **Note Mode**: Support for candidate number recording in cells
* **Highlight Hints**: Highlight same numbers for assistance
* **Error Detection**: Real-time input error detection
* **Undo Function**: Support for undoing previous moves

3. **Game Interface**
* **Professional Sudoku Board**: 9x9 standard grid with clear 3x3 sub-grid division
* **Smart Input System**: Bottom number pad supporting number input and note mode
* **Visual Feedback**: Selected cell highlighting with related cells (row, column, box) highlighting
* **Status Display**: Timer, error counter (heart display), game progress
* **Theme Switching**: Multiple preset themes (green, blue, sakura, red, deep purple)

4. **Game Mechanics**
* **Difficulty Levels**: From beginner to master level
* **Progress Saving**: Independent save for each level
* **Achievement System**: Record solving time and success rate
* **Error Limit**: Maximum 3 errors allowed
* **Haptic Feedback**: Operation vibration feedback

5. **Personalization**
* **Theme Customization**: Multiple preset themes with real-time switching
* **Haptic Settings**: Customizable vibration feedback
* **Interface Optimization**: Dark mode support, customizable font size
* **Operation Habits**: Customizable gestures and operation methods
* **Multilingual**: Support for 18 languages

6. **Technical Features**
* **Performance Optimization**: Smooth gaming experience, low power consumption
* **Offline Mode**: Full offline support
* **Auto-save**: Real-time progress saving
* **Data Security**: Secure user data storage
* **Continuous Updates**: Regular feature optimization and content updates

#### Usage Scenarios

1. **Daily Entertainment**
* **Commute Time**: Solve puzzles during travel
* **Relaxation**: Unwind after work or study
* **Waiting Time**: Pass time while waiting
* **Bedtime Relaxation**: Light game for better sleep
* **Family Entertainment**: Suitable for all ages

2. **Learning and Training**
* **Mathematical Thinking**: Develop logical reasoning
* **Concentration**: Improve focus and attention
* **Memory**: Exercise memory through puzzle solving
* **Thinking Training**: Develop systematic thinking
* **Stress Relief**: Relax through puzzle solving

3. **Professional Training**
* **Sudoku Competition**: Preparation for competitions
* **Brain Training**: Professional brain training tool
* **Solving Techniques**: Learn advanced solving methods
* **Speed Training**: Improve solving speed
* **Difficulty Challenge**: Challenge high-difficulty puzzles