:root {
  --ease-standard: cubic-bezier(.2, .7, .3, 1);
  --dur-tap: 120ms;
  --dur-state: 180ms;
  --dur-sheet: 260ms;
}

/* Interaction model, encoded once:
   hover  → surface lightens (dark) / darkens (light) by ~4% alpha, no motion
   press  → scale(.96), no color change
   select → accent fill + accent glow shadow; idle chips carry a hairline only */