Software Design

This skill provides guidance on software design principles, emphasizing simplicity, maintainability, and clean architecture.

The Four Rules of Simple Design

These rules, in priority order, guide all design decisions:

1. Passes the tests — The code must work correctly
2. Reveals intention — The code clearly expresses what it does
3. No duplication — Every piece of knowledge has a single representation (DRY)
4. Fewest elements — No unnecessary classes, methods, or code

Rules 2 and 3 are closely related and reinforce each other. When they appear to conflict, favor revealing intention — clarity for the reader takes precedence.

The rules are applied in order: never sacrifice correctness for clarity, never sacrifice clarity for DRY, and never add elements just to reduce duplication.

SOLID Principles