.topnav {
  position: sticky;
  top: 0;
  overflow: hidden;
  background-color: #fff;
  border-bottom: 1px solid #000;
  box-shadow: 0 2px 1px 0 gray;
  z-index: 1000;
}
.topnav a {
  float: right;
  display: block;
  color: #6fb352;
  text-align: center;
  padding: 20px;
  text-decoration: none;
  font-size: 18px;
}
.topnav a:hover {
  color: #43328e;
  text-decoration: none;
}
.topnav .icon {
  display: none;
}
@media screen and (max-width: 700px) {
  .topnav a:not(:first-child) {display: none;}
  .topnav a.icon {
    float: right;
    display: block;
  }
  .topnav.responsive .icon {
    position: absolute;
    right: 0;
    top: 0;
  }
  .topnav.responsive a {
    float: none;
    display: block;
    text-align: left;
    clear: both;
  }
}