:root{
  /* Radii are small and deliberate. Highway signage does not have soft corners. */
  --radius-0:0;
  --radius-xs:2px;    /* tags */
  --radius-sm:3px;    /* buttons, nav CTA */
  --radius-md:6px;    /* cards */
  --radius-pill:999px;/* numbered stack badges only */

  --border-width-hair:1px;
  --border-width-cta:1.5px;
  --border-width-rule:2px;
  --border-width-accent:4px;   /* callout left rule */
  --border-width-cap:5px;      /* model card top cap */

  --rule-accent:var(--border-width-accent) solid var(--accent);
  --card-border:var(--border-width-hair) solid var(--border-hairline);
}