/* btnarriba.css */
#btnarriba {
  position: fixed;
  bottom: 20px;
  right: 20px;
  font-size: 20px;
  padding: 0.3em 0.6em;
  border: none;
  background-color:  #4CAF50;
  color: #333;
  border-radius: 4px;
  cursor: pointer;
  box-shadow: 0 2px 5px rgba(0,0,0,0.2);
  display: none; /* Oculto por defecto */
  transition: opacity 0.3s;
  z-index: 1000;
}
#btnarriba:hover {
  background-color: #ddd;
}