Give a fresher-friendly overview of SOLID principles.

SOLID (fresher map)

• Single Responsibility — one reason to change per class.
• Open/Closed — extend via new classes, not editing stable code.
• Liskov — subclasses honor parent expectations.
• Interface Segregation — small interfaces, not fat ones.
• Dependency Inversion — depend on abstractions, inject implementations.

You don't need textbook quotes—show you recognize maintainability pain each letter fixes.