/* Bouton rond "retour en haut" (toutes les pages du site public). Cache
   tant que la page n'a pas ete assez defilee (classe .is-visible posee par
   back-to-top.js). Sans JavaScript il reste cache : rien ne casse. */

.back-to-top {
  position: fixed;
  right: var(--space-5);
  bottom: calc(var(--space-5) + env(safe-area-inset-bottom));
  /* Sous le header (100) et le menu mobile (200), sous les toasts (300). */
  z-index: 90;
  display: grid;
  place-items: center;
  width: 48px;
  height: 48px;
  padding: 0;
  border: 1px solid var(--border-strong);
  border-radius: 50%;
  background: var(--surface-2);
  color: var(--text-primary);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition:
    opacity var(--duration-standard) var(--ease-out),
    transform var(--duration-standard) var(--ease-out),
    visibility 0s linear var(--duration-standard),
    background-color var(--duration-standard) var(--ease-out),
    border-color var(--duration-standard) var(--ease-out);
}

.back-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: none;
  transition-delay: 0s;
}

.back-to-top svg {
  width: 22px;
  height: 22px;
}

@media (hover: hover) and (pointer: fine) {
  .back-to-top:hover {
    background: var(--accent);
    border-color: var(--accent);
  }
}

.back-to-top:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}

@media (prefers-reduced-motion: reduce) {
  .back-to-top {
    transform: none;
    transition: none;
  }
}