#backToTopBtn {
  display: none;
  position: fixed;
  bottom: 30px;
  right: 40px;
  z-index: 99;
  font-size: 18px;
  border: none;
  outline: none;
  background-color: #555;
  color: white;
  cursor: pointer;
  padding: 15px;
  border-radius: 30%;
}

#backToTopBtn:hover {
  background-color: #333;
}