Building layout and visual systems in CSS that survive real content. Covers choosing between flexbox and grid, responsive design driven by content rather than device breakpoints, cascade layers and specificity discipline, custom properties as design tokens, dark mode, container queries, and avoiding forced synchronous layout. Use when building a page or component layout, when a stylesheet has become an override war, when a design needs to work across viewports and themes, or when scrolling and animation feel janky.
