What problem does it solve? Building consistent, maintainable UI foundations across web and mobile applications is difficult when colors, spacing, and component styles are hardcoded and scattered. This Skill provides proven patterns for design tokens, theme switching, and component architecture so teams can establish scalable design system foundations. ## Core Features & Use Cases - Design Token Hierarchies: Structure primitive, semantic, and component tokens with CSS custom properties and Style Dictionary pipelines for multi-platform output (CSS, SCSS, iOS Swift, Android XML). - Theming Infrastructure: Implement light/dark theme switching with React context providers, system preference detection, localStorage persistence, and multi-brand theming. - Component Architecture: Apply compound components, polymorphic components, slot patterns, headless hooks, and CVA-based variant systems for flexible component APIs. - Use Case: When building a component library that must support light and dark modes across web and mobile, use this Skill to define a token hierarchy, wire up a ThemeProvider, and generate platform-specific token outputs via Style Dictionary. ## Quick Start Ask the AI to create a design token system with light and dark theme support using CSS custom properties and a React ThemeProvider.