#preview {
    position: fixed;
    background: rgba(105, 105, 105, 0.8);
    color: #fff;
    width: 100%;
    height: 100%;
    z-index: 2000;
    top: 0px;
    left: 0px;
}

.loading {
    position: absolute;
    left: 47.5%;
    top: 46%;
}

#button_bar {
    position: absolute;
    top: 0px;
}