.clickable {cursor: pointer;}
.topnav {
  background-color: #333;
  overflow: hidden;
  position: -webkit-sticky;
  position: sticky;
  top: 0;
}


.topnav a {
  float: left;
  color: #f2f2f2;
  text-align: center;
  padding: 20px 75px;
  text-decoration: none;
  font-size: 30px;
}


.topnav a:hover {
  background-color: #ddd;
  color: black;
}


.topnav a.active {
  background-color: tomato;
  color: white;
}