lib/web/htdocs/modules/backdrop/style.css

.backdropContainer {
    contain: style size;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: -1;
    touch-action: none;
}
.backdropImage {
    background-repeat: no-repeat;
    background-position: center center;
    -webkit-background-size: cover;
    background-size: cover;
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    contain: strict;
}
.backdropImageFadeIn {
    -webkit-animation: backdrop-fadein 0.8s ease-in-out normal both;
    animation: backdrop-fadein 0.8s ease-in-out normal both;
}
@-webkit-keyframes backdrop-fadein {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}
@keyframes backdrop-fadein {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}