What problem does it solve? Codebases accumulate design debt when principles like DRY, SOLID, and separation of concerns are applied inconsistently or only remembered after problems surface. This Skill enforces a mandatory design lens during planning, implementation, and review so violations are caught before they ship. ## Core Features & Use Cases - Principle Enforcement: Covers DRY, KISS, YAGNI, SoC, loose coupling, high cohesion, Law of Demeter, CQS, composition over inheritance, Fail Fast, POLA, and full SOLID with violation/fix tables and test questions for each. - GoF Pattern Guidance: Maps code smells (god class, telescoping constructor, switch-on-type) to the correct creational, structural, or behavioral pattern, including confused-pair comparisons and pattern evolution triggers. - Planning & Review Checklists: Provides runnable checklists that integrate with plan-writing, plan-execution, and code-review workflows, plus conflict-resolution rules (e.g., DRY vs YAGNI decided by the Rule of Three). - Use Case: While reviewing a pull request, run the Review Checklist to catch a method that both mutates state and returns data (CQS violation), a subclass breaking its base contract (LSP), or a new ad-hoc branch bolted onto an unrelated flow. ## Quick Start Ask the AI to apply design-principles to review the current module's class structure and flag any SOLID or coupling violations.
