:root{
  /* Artifact draws, it does not float: rules and hard edges, no soft shadows. */
  --radius-none:0;
  --radius-sm:0;      /* the system is square by default */
  --radius-pill:999px; /* reserved for wayfinding dots / status only */

  --rule-hairline:1px;
  --rule-standard:2px;
  --rule-heavy:4px;
  --rule-structural:8px;

  --border-default:var(--rule-hairline) solid var(--border-hairline);/* @kind other */
  --border-strong:var(--rule-standard) solid var(--border-rule);/* @kind other */
  --border-frame:var(--rule-heavy) solid var(--border-rule);/* @kind other */

  /* Elevation is used sparingly, and only on interactive overlays. */
  --shadow-none:none;
  --shadow-overlay:0 24px 48px -16px rgba(0,0,0,.28);
  --focus-ring:0 0 0 2px var(--surface-page),0 0 0 4px var(--ink-blue);
}