.back{
  position: fixed;
  top: 20px;
  right: 30px;
  display: none;
  z-index: 99;
  font-size: 20px;
  border: none;
  outline: none;
  background-color: #04AA6D ;
  color: white;
  cursor: pointer;
  border-radius: 20px;
  height: 40px;
  width: 40px;
  font-weight: bolder;
  text-align: center;
  line-height: 40px;
}

#topBtn {
  display: none;
  position: fixed;
  bottom: 20px;
  right: 30px;
  z-index: 99;
  font-size: 20px;
  border: none;
  outline: none;
  background-color: #04AA6D ;
  color: white;
  cursor: pointer;
  border-radius: 20px;
  height: 40px;
  width: 40px;
  font-weight: bolder;
}

#topBtn:hover, .back:hover {
  background-color: #555;
}