.mask{
    background-color: rgba(0,0,0,.75);
    position: fixed;
    left: 0;
    top: 0;
    z-index: 90000;
    width:100%;
    height:100%;
}
.popup{
    position: fixed;
    left: 50%;
    top: 50%;
    z-index: 99999;
    -webkit-transform: translate(-50%,-50%);
    transform: translate(-50%,-50%);
    /*max-width:500px;*/
}
.btn-group{
    line-height:60px;
    background:#282828;
    width: 100%;
}
.btn-group ul{
    width: 100%;
}
.btn-group ul li{
    float:left;
    width:50%;
}
.btn-group ul li:first-child{
    border-right:1px solid #2c2b2b;
}
.btn-group ul:after{
    display:block;
    content:'';
    clear:both;
}
.btn-group ul li button{
    display:block;
    text-align:center;
    width:100%;
    border:0;
    background:#111;
    color:#fff;
    height:60px;
    line-height:60px;
    font-size:1.6rem;
}
.btn-group ul li button:active{
    background:#000;
}
.popup{
    position: fixed;
    left: 50%;
    top: 50%;
    z-index: 99999;
    -webkit-transform: translate(-50%,-50%);
    transform: translate(-50%,-50%);
    /*max-width:500px;*/
}

@media screen and (max-width: 500px) { /*iPhone 6/7/8 plus*/
    .popup{
        width:80%;
    }
    .btn-group ul li button{
        height:50px;
        line-height:50px;
        font-size:1.4rem;
    }
}

img{
    max-width:100%;
    height:auto;
    /*display:block;*/
}