🎮 Cut The Rope

A physics-based puzzle game where you cut ropes to guide a candy ball into a target box.

Game Design Presentation • Play Now

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📸 Overview

Cut The Rope is a puzzle game that challenges players to use physics and timing to solve levels. The candy hangs from ropes attached to anchors - your job is to cut the ropes at the right moment to let gravity and momentum guide the candy into the target box.

Built with Python, pygame-ce, and pymunk for realistic 2D physics simulation.

✨ Key Features

• 🔗 Realistic Rope Physics - Chains swing and respond to cuts naturally using Pymunk physics engine
• 🎯 Progressive Difficulty - 6 handcrafted levels introducing new mechanics gradually
• ⚡ Responsive Controls - Cut ropes with mouse slashes or keyboard letters
• 🎨 Clean Visual Design - Dark space theme with vibrant colors and particle effects
• 🛠️ Built-in Level Editor - Create and share your own custom levels
• 🔄 Quick Reset - Instantly retry levels with the R key

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🚀 Getting Started

Prerequisites

• Python 3.10 or higher
• pip (Python package installer)

Installation

1. Clone the repository:

git clone https://github.com/yourusername/cut-the-rope.git
cd cut-the-rope

2. Create a virtual environment (recommended):

python -m venv .venv
source .venv/bin/activate  # On Windows: .venv\Scripts\activate

3. Install dependencies:

pip install -r requirements.txt

🎮 How to Play

Run the game:

python run.py

Objective

Cut the ropes holding the candy to swing and drop it into the green target box. The candy must settle (stay inside for 2 seconds) to win!

Controls

Action	Key/Mouse
Cut Rope	Mouse drag / Letter keys (A, B, C...)
Restart Level	R
Toggle Instructions	I
Level Select	1-6 number keys
Quit	ESC

Strategy Tips

1. Observe the rope configuration and target location
2. Plan which rope to cut first to create the right swing
3. Time your cuts to use momentum and gravity effectively
4. Avoid red spike hazards - they reset the level!
5. Use platforms to bounce and redirect the candy

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🎯 Levels

Level	Description	Challenge
Level 1	Simple Drop	Learn the basic mechanic - cut the single rope
Level 2	Double Swing	Use momentum from two ropes to reach the target
Level 3	Obstacle Course	Navigate around platforms and barriers
Level 4	Precision	Time your cuts perfectly for the right arc
Level 5	Hazard Warning	Avoid deadly spikes while solving the puzzle
Level 6	Master Challenge	Combine all skills in a complex multi-rope setup

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🛠️ Level Editor

Create your own puzzles with the built-in visual level editor!

Running the Editor

python level_editor.py

Editor Controls

Key	Action
1	Place Candy (starting position)
2	Place Anchor (rope attachment point)
3	Place Target Box (click twice for corners)
4	Place Platform (click twice for corners)
5	Place Spike (hazard)
Left Click	Place selected object
Right Click	Delete object at mouse
S	Print level code to console
C	Clear all objects
ESC	Quit editor

Adding Your Level

1. Design your level in the editor
2. Press S to get the level code
3. Copy the generated LevelData code
4. Open src/levels.py
5. Paste it into the _create_levels() method
6. Add it to the return list

# Example in src/levels.py
def _create_levels():
    level_1 = LevelData(
        candy_pos=(600, 450),
        anchors=[...],
        target=...
    )

    your_level = LevelData(
        candy_pos=(600, 400),
        anchors=[(700, 600, 'A'), (500, 600, 'B')],
        ...
    )

    return [level_1, level_2, your_level]

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🏗️ Architecture

Project Structure

cut-the-rope/
├── src/
│   ├── config.py          # Game configuration & constants
│   ├── entities.py        # Entity classes (Candy, Rope, etc.)
│   ├── game.py            # Main game loop & state management
│   ├── levels.py          # Level definitions
│   ├── physics.py         # Pymunk physics engine wrapper
│   ├── renderer.py        # Pygame rendering
│   ├── ui.py              # UI components & menus
│   └── utils.py           # Utility functions
├── level_editor.py        # Visual level editor
├── run.py                 # Game entry point
├── requirements.txt       # Python dependencies
├── README.md              # This file
└── cut-the-rope-presentation.html  # Game Design Analysis

Technical Details

Physics Engine (Pymunk)

• Gravity: -900 px/s² (downward acceleration)
• Sub-stepping: 4 physics steps per frame for stability
• Rope Simulation: PinJoint constraints with damping
• Collision: Category-based collision filtering

Coordinate Systems

• Pymunk: Bottom-left origin (Y increases upward)
• Pygame: Top-left origin (Y increases downward)
• Conversion: pygame_to_pymunk() and pymunk_to_pygame() utilities

Rope Cutting Algorithm

def line_segment_intersection(p1, p2, p3, p4):
    """Check if line segment (p1,p2) intersects (p3,p4)"""
    # Uses standard line intersection formula
    # Returns True if lines cross, False otherwise

Win Detection

1. Collision sensor detects candy entering target
2. Timer starts when candy is inside
3. Candy must have velocity < 80 px/s (settled)
4. Win after 2 seconds of continuous settlement

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🎨 Game Design

This game was developed as part of a Game Design course, analyzing core game design principles:

• MDA Framework: Mechanics → Dynamics → Aesthetics
• Bartle Player Types: Targeted at Achievers & Explorers
• Flow Theory: Progressive difficulty maintains player engagement
• Schema Theory: Teaching patterns through level progression

View the full Game Design Analysis Presentation for an in-depth look at the design decisions behind Cut The Rope.

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🧪 Testing

Run the test suite:

python -m pytest uniTest/

Or run specific tests:

python -m pytest uniTest/test_physics.py -v

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📚 Dependencies

Package	Version	Description
pygame-ce	≥2.4.1	Modern Python game library
pymunk	≥6.5.0	2D physics engine based on Chipmunk

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🤝 Contributing

Contributions are welcome! Feel free to:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Ideas for Contributions

• 🌟 New levels (easy, medium, hard)
• 🎨 New visual themes or skins
• 🚧 New obstacle types (springs, fans, teleports)
• 🏆 Achievement system
• 📊 Level statistics and analytics
• 🎵 Sound effects and music

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👥 Team

Developed by:

• Muhammad Yaseen
• Hevar Hemin
• Revar Azim

Supervisor: Mrs. Rina D. Zarro

Course: Game Design - University of Salahaddin - Erbil

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📄 License

This project is open source and available under the MIT License.

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🙏 Acknowledgments

• Pymunk - Excellent 2D physics engine
• Pygame-ce - Modern community-driven Pygame fork
• Cut the Rope (ZeptoLab) - Inspiration for this project
• Game Design course materials and lectures

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Enjoy the game! 🎮

Report Bug • Request Feature • Game Design Presentation