nav {
  display: block;
  width: 80%;
  margin: 0px auto;
  height: 50px;
  webkit-box-shadow: 0px 0px 11px 4px rgba(0,0,0,0.75);
  -moz-box-shadow: 0px 0px 11px 4px rgba(0,0,0,0.75);
  box-shadow: 0px 0px 11px 4px rgba(0,0,0,0.75);
  font-weight: bold;
}

ul.topnav {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #333;
}

ul.topnav li {float: left;}

ul.topnav li a {
  display: inline-block;
  color: #f2f2f2;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
  transition: 0.3s;
  font-size: 17px;
}

ul.topnav li a:hover {background-color: #555;}

ul.topnav li.icon {display: none;}

@media screen and (max-width:680px) {
  ul.topnav li {display: none;}
  ul.topnav li.icon {
    float: left;
    display: inline-block;
  }
}

@media screen and (max-width:680px) {
nav {
  width: 100%;
}
ul.topnav.responsive {position: relative;}

ul.topnav.responsive li {
  float: none;
  display: inline;
}
ul.topnav.responsive li a {
  display: block;
  text-align: left;
}
}