 {
          height: 40px;
          line-height: 40px;
          padding: 0 20px;
          border-bottom: 1px solid #ccc;
        }
        
        .list > *.core-selected {
          background: #333;
        }
        
        li {
          height: 30px;
        }
        
        li.core-selected:after {
          content: "\2713";
          position: absolute;
          padding-left: 10px;
        }
      </style>
      
      <h2>basic</h2>
      <core-selector class="list" selected="0">
        <d