HTML  a {
    position: relative;
    text-decoration: none;
    display: block;
    text-align: center;
    width: 200px;
}

/* 绘制上下线条 */
a::before,
a::after{
    content: "";
    position: absolute;
    width: 100%;
    height: 2px;
    transition: width .2s ease-in-out;
    background: #92B901;
}

/* 固定线条方向 */
a::before{
    top: 0;
    left: 0;
}
a::after{
    bottom: 0;
    right: 0;
}

/* 过滤效果 */
a:hover::before,
a:hover::after{
    width: 0;
}


a span{
    display: block;
    padding: 20px;
}

/* 绘制左右线条 */
a span::before,
a span::after{
    content: "";
    position: absolute;
    width: 2px;
    height: 100%;
    transition: height .2s ease;
    background: #92B901;
}
a span::before{
    bottom: 0;
    left: 0;
}
a span::after{
    top: 0;
    right: 0;
}
a span:hover::before,
a span:hover::after{
    height: 0;
}