What problem does it solve? Frontend codebases drift visually when developers introduce ad-hoc patterns, inconsistent animations, or off-brand components. This Skill keeps every UI change aligned with the existing design system by enforcing concrete styling rules before and during implementation. ## Core Features & Use Cases - Design System Enforcement: Requires reusing theme tokens, breakpoints, and primitives from apps/web/src/components/ instead of inventing new controls or surfaces. - Motion and Interaction Rules: Defines allowed hover/press expressions, transition durations, easing curves, and prefers-reduced-motion handling so animations stay consistent and accessible. - Structured UI Reviews: Produces focused review feedback in a Before | After | Why markdown table verified against real rendered surfaces, viewport sizes, keyboard focus, and reduced motion. - Use Case: When adding a new settings panel to the TanStack Start web app, the Skill ensures you reuse existing primitives, CSS modules, and breakpoint variables rather than introducing raw media queries or new button styles. ## Quick Start Review my new profile page component and make its styling consistent with the existing design system.