/* Shared stack scroll — overlapping sticky layers */
:root {
  --stack-nav: 2.5rem;
  --stack-stick: 3rem;
  --stack-step: 2.75rem;
  --stack-tab-h: 2.25rem;
  /* Height of tab rail (all L0–L6 tabs visible) */
  --stack-reveal: calc(var(--stack-stick) + var(--stack-step) * 6 + var(--stack-tab-h));
  --stack-slot: 100vh;
  --stack-slot-last: 50vh;
  --stack-pull: calc(var(--stack-slot) - var(--stack-reveal));
  --stack-body-h: calc(100dvh - var(--stack-reveal) - 1rem);
}