/* =========================================================
   Back to top — comparsa dopo scroll, bottom-right.
   Restrained: superficie scura paper-ink, ink-on-dark, no shadow gratis.
   Motion: solo transform + opacity (mai layout).
   ========================================================= */
.mz-back-to-top {
  position: fixed;
  right: clamp(12px, 2.5vw, 24px);
  bottom: clamp(12px, 2.5vw, 24px);
  z-index: 90;

  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  padding: 0;

  background: var(--paper-ink);
  color: var(--ink-on-dark);
  border: 1px solid var(--border-on-dark);
  border-radius: 4px;
  cursor: pointer;

  opacity: 0;
  transform: translateY(8px);
  pointer-events: none;
  visibility: hidden;
  transition:
    opacity 240ms cubic-bezier(0.22, 1, 0.36, 1),
    transform 240ms cubic-bezier(0.22, 1, 0.36, 1),
    visibility 0s linear 240ms,
    border-color 160ms ease-out,
    background-color 160ms ease-out;
}

.mz-back-to-top.is-visible {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
  visibility: visible;
  transition:
    opacity 240ms cubic-bezier(0.22, 1, 0.36, 1),
    transform 240ms cubic-bezier(0.22, 1, 0.36, 1),
    visibility 0s linear 0s,
    border-color 160ms ease-out,
    background-color 160ms ease-out;
}

.mz-back-to-top:hover {
  border-color: var(--border-on-dark-strong);
  /* Solleva paper-ink uniformemente in entrambi i temi — niente hex hardcoded. */
  background: color-mix(in oklab, var(--paper-ink) 85%, white);
}

.mz-back-to-top:focus-visible {
  outline: 2px solid var(--brand);
  outline-offset: 2px;
}

.mz-back-to-top:active {
  transform: translateY(0) scale(0.96);
}

.mz-back-to-top__icon {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  stroke-width: 2;
  fill: none;
  stroke-linecap: round;
  stroke-linejoin: round;
}

@media (prefers-reduced-motion: reduce) {
  .mz-back-to-top,
  .mz-back-to-top.is-visible {
    transition: opacity 0s, visibility 0s;
    transform: none;
  }
  .mz-back-to-top:active {
    transform: none;
  }
}