/* Bouton "retour haut" */
.back-to-top{
  position: fixed !important;
  right: 24px !important;
  bottom: 24px !important;
  z-index: 2000 !important;

  width: 52px;
  height: 52px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 8px rgba(0,0,0,.3);

  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transition: opacity .2s ease, visibility .2s ease;
}
.back-to-top.show{
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
}