#myBtn {
  opacity: 0;
  position: fixed;
  bottom: 80px;
  /* right: 30px; */
  right: 40px;
  z-index: 99;
  font-size: 20px;
  border: none;
  outline: none;
  background: #111;
  color: #fff;
  cursor: pointer;
  padding: 10px;
  width: 60px;
  height: 60px;
  border-radius: 50%;
  transition: 0.5s
}

#myBtn:hover {
  box-shadow: rgba(100, 100, 111, 0.2) 0px 7px 29px 0px;
}