#btnTopo {
  position: fixed;
  bottom: 20px;
  right: 20px;
  display: none;
  background-color: #4CAF50;
  color: #fff;
  border-color: #333;
  padding: 12px 16px;
  border-radius: 50%;
  cursor: pointer;
  font-size: 30px;
}

#btnTopo:hover {
  background-color: #45a049;
}