ul, #myUL
        {
            list-style-type: none;
        }
         
        #myUL
        {
            margin: 0;
            padding: 0;
        }
         
        .box
        {
            cursor: pointer;
            -webkit-user-select: none; /* Safari 3.1+ */
            -moz-user-select: none; /* Firefox 2+ */
            -ms-user-select: none; /* IE 10+ */
            user-select: none;
        }
         
        .box::before
        {
            content: "+";
            color: black;
            display: inline-block;
            margin-right: 6px;
        }
         
        .check-box::before
        {
            content: "-";
        }
         
        .nested
        {
            display: none;
        }
         
        .active
        {
            display: block;
        }