.show_download_center{
    display: none;
}

.download-center{
    position: fixed;
    right: 20px;
    bottom: 70px;
    line-height: 20px;
    width: 50px;
    height: 50px;
    background: #1E6FFA;
    border-radius: 4px;
    color: #fff;
    font-size: 14px;
    padding: 4px 11px;
    cursor: pointer;
    z-index: 1000;
    letter-spacing: 0;
}
.download-center + div>.dawnload_maskDiv{
    z-index: 9;
}