Subsystem Classes (Amplifier, DVDPlayer):?

Short answer: These classes represent the components of the complex subsystem. They have specific functionalities but are complicated to interact with individually. Amplifier: public class Amplifier

Example code

{
public void On() => Console.WriteLine("Amplifier is on.");
public void Off() => Console.WriteLine("Amplifier is off.");
} DVDPlayer: public class DVDPlayer
{
public void Play(string movie) => Console.WriteLine($"Playing {movie}."); }

Real-world example (ShopNest)

Use a GoF pattern in ShopNest only when it removes duplication or makes a change safer—explain the problem it solves in the interview.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.