body {
    /* min-width: 320px; */
    max-width: 750px;
    /* flexible  10 */
    width: 10rem;
    height: 20.8rem;
    margin: 0 auto;
    font-family: Arial, Helvetica;
    background:white;
}

.app {
    height: 100%;
    width: 100%;
    background: url(../images/download1/index3.jpg) no-repeat;
    background-size: 100%;
    position: relative;
}


.btn-d {
    width: 4.98rem;
    margin-top: 8.45rem;
    height: 1.94rem;
}


.btn-down {
    position: absolute;
    top: 2.82rem;
    right: 2.86rem;
    width: 4.22rem;
    height: 4.22rem;
}