---
name: css
description: CSS3 styling conventions, responsive design, custom properties, and layout patterns. Use when writing or editing .css files, responsive design, CSS custom properties, or styling without a framework.
---

# CSS

- Use a consistent naming convention (BEM or utility-first).
- Mobile-first responsive design.
- Prefer CSS custom properties over preprocessor variables.
- Avoid `!important`; fix specificity instead.