#back-to-top {
  position: fixed;
  bottom: 20px;
  right: 20px;
  display: none;
  background-color: #e35e5e;
  color: #fff;
  padding: 10px;
  border-radius: 5px;
  text-align: center;
  cursor: pointer;
}

#back-to-top:hover {
  background-color: #555;
}