.demo1{            position: relative;            text-decoration: none;            font-size: 20px;            color: #333;        }        .demo1:before{            content: "";            position: absolute;            left: 50%;            bottom: -2px;            width: 0;            height: 2px;            background: #4285f4;            transition: all .3s;        }        .demo1:hover:before{            width: 100%;            left: 0;            right: 0;        }