What problem does it solve? Choosing and correctly implementing a design pattern is error-prone from memory alone: commonly confused pairs like Strategy/State or Decorator/Proxy share nearly identical structure but solve different problems, and patterns are frequently applied prematurely, adding indirection the code never needed. This Skill provides a vetted catalog of the 22 classic Gang-of-Four patterns with symptom-based lookup so the right pattern is matched to an actual, present-tense problem. ## Core Features & Use Cases - Symptom-based pattern lookup: Three tables (Creational, Structural, Behavioral) map concrete code symptoms like "telescoping constructor" or "state-checking conditionals duplicated across methods" to the matching pattern. - Detailed reference files: Each pattern has a dedicated reference with intent, problem, solution, structure, a TypeScript code example, applicability signals, and explicit "when NOT to use" pitfalls. - Confusion-pair disambiguation: Relations sections explicitly distinguish commonly mixed-up patterns (Strategy vs State, Decorator vs Proxy, Adapter vs Bridge, Facade vs Mediator). - Use Case: When refactoring a checkout flow where an Order object's behavior branches on its status everywhere, the symptom table points to the State pattern, and its reference file provides the structure, example, and transition pitfalls before any code is written. ## Quick Start Ask the assistant to apply a design pattern to your code, for example: "Refactor this class using the Strategy pattern" or "What pattern fits this problem?"
