#container {
     margin: 50px;
 }

 body {
     margin: 0;
     font-family: 'Roboto', "Helvetica", Arial, sans-serif;
     color: #263238;
     display: grid;
     align-items: center;
     text-align: center;
 }

 .topnav {
     overflow: hidden;
     background-color: #263238;
 }

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

 .topnav a.active {
   color: #263238;
 }

 .active {
     background-color: #81c784;
 }

 .topnav .icon {
     display: none;
 }

 .dropdown {
     float: left;
     overflow: hidden;
 }

 .dropdown .dropbtn {
     font-size: 17px;
     border: none;
     outline: none;
     color: white;
     padding: 14px 16px;
     background-color: inherit;
     font-family: inherit;
     margin: 0;
 }

 .dropdown-content {
     display: none;
     position: absolute;
     background-color: #f9f9f9;
     min-width: 160px;
     box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
 }

 .dropdown-content a {
     float: none;
     color: black;
     padding: 12px 16px;
     text-decoration: none;
     display: block;
     text-align: left;
 }

 .topnav a:hover,
 .dropdown:hover .dropbtn {
     background-color: #555;
     color: white;
 }

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

 .dropdown:hover .dropdown-content {
     display: block;
 }

 @media screen and (max-width: 600px) {
     .topnav a:not(:first-child),
     .dropdown .dropbtn {
         display: none;
     }
     .topnav a.icon {
         float: right;
         display: block;
     }
 }

 nav ul li a:active,
 nav ul li a.current {
     border-top-color: green;
     background: #1b435e;
     position: relative;
     top: 1px;
 }

 @media screen and (max-width: 600px) {
     .topnav.responsive {
         position: relative;
     }
     .topnav.responsive .icon {
         position: absolute;
         right: 0;
         top: 0;
     }
     .topnav.responsive a {
         float: none;
         display: block;
         text-align: left;
     }
     .topnav.responsive .dropdown {
         float: none;
     }
     .topnav.responsive .dropdown-content {
         position: relative;
     }
     .topnav.responsive .dropdown .dropbtn {
         display: block;
         width: 100%;
         text-align: left;
     }
 }

 #center {
     align-self: center;
     align-items: center;
     text-align: center;
 }

 .center {
     display: block;
     margin-left: auto;
     margin-top: 50px;
     margin-right: auto;
 }

 #spinner {
   width: 40px;
   height: 40px;
 }