#myBtn {
  display: none; 
  position: fixed; 
  bottom: 20px; 
  right: 30px; 
  z-index: 99; 
  border: none; 
  outline: none; 
  background-color: #006837; 
  color: white; 
  cursor: pointer; 
  padding: 15px; 
  border-radius: 10px; 
  font-size: 18px; 
}

#myBtn:hover {
  background-color: #555; 
}