Initial open source release with CC BY-NC-SA 4.0 license

- Add complete CC BY-NC-SA 4.0 International License
- Add comprehensive README with project description and usage
- Add CONTRIBUTING guidelines for developers
- Add Nix development environment with OpenSCAD tooling
- Add .gitignore for OpenSCAD and Nix projects
- Add copyright headers to source files

README.md

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+# Cuatro - 3D Printable Game Pieces
+
+Cuatro is a collection of 3D printable game pieces designed for board games. The pieces include tubes and boxes with various configurations optimized for game play.
+
+## Features
+
+- **Tubes**: Cylindrical game pieces with hollow centers
+- **Boxes**: Square-based pieces with hollow centers
+- **Customizable**: Configurable dimensions based on board square size
+- **Print-friendly**: Designed for easy 3D printing with minimal support
+
+## Requirements
+
+- [OpenSCAD](https://openscad.org/) for viewing and modifying the design
+- 3D printer capable of printing PLA/PETG/ABS materials
+- Recommended print settings: 0.2mm layer height, 15% infill
+
+## Usage
+
+### Viewing the Model
+
+1. Install OpenSCAD
+2. Open `parts.scad` in OpenSCAD
+3. Press F5 to preview or F6 to render
+
+### Printing
+
+The design generates four different types of pieces:
+- **Row 1**: Tube holes (negative space for creating molds)
+- **Row 2**: Solid tubes
+- **Row 3**: Solid boxes  
+- **Row 4**: Box holes (negative space for creating molds)
+
+Print recommendation: Create two copies in different colors for game play.
+
+### Customization
+
+Key parameters in `parts.scad`:
+- `board_square_size_in_mm`: Base dimension (default: 26mm)
+- `star_width`: Piece width as ratio of board square (default: 0.4)
+- `default_height`: Piece height as ratio of board square (default: 1.9)
+
+## File Structure
+
+```
+cuatro/
+├── parts.scad          # Main OpenSCAD file with all piece definitions
+├── README.md           # This file
+├── LICENSE            # CC BY-NC-SA 4.0 license
+└── CONTRIBUTING.md    # Guidelines for contributors
+```
+
+## Contributing
+
+We welcome contributions! Please see [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines on:
+- Reporting bugs
+- Suggesting enhancements
+- Submitting pull requests
+- Code style guidelines
+
+## License
+
+This project is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License (CC BY-NC-SA 4.0).
+
+You are free to:
+- **Share** — copy and redistribute the material in any medium or format
+- **Adapt** — remix, transform, and build upon the material
+
+Under these conditions:
+- **Attribution** — Give appropriate credit and indicate if changes were made
+- **NonCommercial** — You may not use the material for commercial purposes
+- **ShareAlike** — Distribute contributions under the same license
+
+See the [LICENSE](LICENSE) file for full details or visit https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+## Support
+
+For questions, issues, or feature requests, please open an issue in this repository.