*{
    margin:0;
    padding:0;
}

.center{
    width:100%;
    max-width:750px;
    margin:0 auto;
    position:relative;
}

.bg{
    width:100%;
    display:block;
}

.product{
    position:absolute;
    bottom:40px;
    width:100%;
    text-align:center;
}

.product ul{
    display:flex;
    flex-wrap:wrap;
    justify-content:center;
}

.product li{
    width:50%;          /* 一行两个 */
    list-style:none;
    text-align:center;
    margin:10px 0;
}

.product a{
    position:relative;
    display:inline-block;
}

.product img{
    width:90%;
    max-width:260px;
}