CSS gains a class prefix selector: one `.btn-*` rule replaces six lines
CSS Selectors Level 5 just adopted a wildcard that matches every class with a given prefix — `.btn-*` hits `.btn-primary`, `.btn-secondary`, and friends in a single rule. Today you'd hand-list each variant or lean on slow substring selectors like `[class^="btn-"]`. The ergonomics are great, but you'll need `@supports selector(.btn-*)` until the feature becomes Baseline.