body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
    height:200vh;
}

.topnav {
  position: sticky;
  top: 0;
  overflow: hidden;
  background-color: #333;
        z-index: 4;
}

.topnav a {
  float: left;
  color: #f2f2f2;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
  font-size: 17px;
}

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

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

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

.topnav span{
  float: right;
   color: #f2f2f2;
   text-align: center;
     padding: 14px 16px;
}