#scan_actions #scan_stop {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    z-index: 2;
}
#scan_actions #scan_reader {
    display: none;
}
#scan_actions.scanning #scan_stop {
    display: inline-block;
}
#scan_actions.scanning #scan_reader {
    display: block;
}
#scan_actions.scanning #scan_start {
    display: none;
}
#scan_reader {
    position: fixed !important;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    max-height: 500px;
    max-width: 500px;
    z-index: 1;
}