.back-to-top {
  background-color: #cb3232;
  text-decoration: none;
  cursor: pointer;
  width: 35px;
  height: 35px;
  z-index: 999;
  position: fixed;
  right: 15px;
  bottom: 15px;
  opacity: .5;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 0;
}
.back-to-top:hover {
  background-color: #cb3232;
  opacity:.90;
}

.back-to-top svg.icon__arrow-up {
  fill: white;
  width: 18px;
  height: 18px;
  opacity: .75;
}