/* Walnut disc parked at the fold — a quiet way home, never a chunky UI chip.
   It arrives with the compact header: hidden at the top, in once the bar settles. */
.back-top {
  position: fixed;
  right: max(1.25rem, env(safe-area-inset-right));
  bottom: max(1.25rem, env(safe-area-inset-bottom));
  z-index: 90;
  display: grid;
  place-items: center;
  width: 2.4rem;
  height: 2.4rem;
  border-radius: 50%;
  background: var(--color-accent);
  color: var(--color-accent-contrast);
  text-decoration: none;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transform: translateY(0.5rem);
  filter: blur(4px);
  transition:
    opacity var(--duration-ui) var(--ease-out),
    transform var(--duration-ui) var(--ease-out),
    filter var(--duration-ui) var(--ease-out),
    visibility var(--duration-ui),
    background-color var(--duration-ui) var(--ease-out);
}

.site-header-overlay.is-compact ~ .back-top {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: none;
  filter: none;
}

.back-top svg {
  width: 0.95rem;
  height: 0.95rem;
}

.back-top:hover,
.back-top:focus-visible {
  background: var(--color-accent-hover);
}