.back-to-top {
  box-shadow: var(--spruce-shadow-lg);
  inset-block-end: 1.5rem;
  inset-inline-end: 1.5rem;
  opacity: 0;
  position: fixed;
  translate: 0 1rem;
  visibility: hidden;
  z-index: 1030;
  transition-duration: var(--spruce-duration);
  transition-property: opacity, translate, visibility;
  transition-timing-function: var(--spruce-timing-function);
}
.back-to-top.is-visible {
  opacity: 1;
  translate: 0 0;
  visibility: visible;
}