.back-to-top {
  display: none;
  position: fixed;
  bottom: 40px;
  right: 40px;
  z-index: 9999;
  font-size: 18px;
  color: #FCFCFCf;
  background-color: #3E4755;
  border: none;
  outline: none;
  cursor: pointer;
  padding: 8px;
  border-radius: 12px;
}
 
.back-to-top:hover {
  background-color: #3E4755;
}
 
.visible {
  display: flex;
}