css

The @layer rule introduces explicit layers to the CSS cascade, allowing developers to control style priority by layer order rather than specificity — solving specificity wars in large codebases without resorting to !important.

Container queries let components adapt their styling based on the size of their parent container rather than the viewport — enabling truly reusable responsive components that work in any layout context.

CSS performance spans the rendering pipeline stages of style calculation, layout, paint, and compositing — with optimization strategies including critical CSS extraction, CSS containment, efficient selector patterns, and minimizing layout-triggering property changes.