Write consistent, maintainable CSS using the project's methodology (Tailwind, BEM, CSS Modules) with proper design tokens and performance optimization. Use this skill when writing or modifying styles, CSS classes, Tailwind utilities, or styling-related code. When working on files like *.css, *.scss, *.module.css, tailwind.config.js, or components with inline/utility styles. When applying design system tokens (colors, spacing, typography), avoiding framework style overrides, or optimizing CSS for production with purging/tree-shaking.