Level 3 — Advanced

These lessons cover the full cascade, cascade layers, native nesting, modern color functions, scoping, CSS architecture with BEM, utility-first CSS and Tailwind, Sass, PostCSS and build tools, rendering performance, accessibility, anchor positioning and view transitions, feature queries and progressive enhancement, and testing and debugging CSS. Recommended: the Level 2 lessons, especially specificity, Grid, custom properties, and responsive design.