solid.md

1. Single Responsibility Principle (SRP) - eliminating duplications and making sure that our pieces are named appropriately and expressively.
2. Open-Closed Principle (OCP) - isolating knowledge, naturally building only the extension points that truly represent the pieces of system that will change.
3. Liskov Substitution Principle (LSP) - only extend derived types don't change base behaviours.
4. Interface Segregation Principle (ISP) - interfaces should be small, focused on a specific use case. Provide a clear, cohesive view of what class does.
5. Dependency Inversion Principle (DIP) - depend on abstraction rather than implementation.