.back-to-top {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  width: 2.5rem;
  height: 2.5rem;
  border: none;
  border-radius: 50%;
  background: rgba(0, 0, 0, 0.8);
  color: #fff;
  font-size: 1.4rem;
  line-height: 1;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-pack: center;
  -ms-flex-pack: center;
  justify-content: center;
  -webkit-box-align: center;
  -ms-flex-align: center;
  align-items: center;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  -webkit-transition: opacity 0.2s ease-in-out, visibility 0.2s ease-in-out;
  transition: opacity 0.2s ease-in-out, visibility 0.2s ease-in-out;
  z-index: 1000;
}

.back-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
}

.back-to-top:hover {
  background: #000;
}