html,
body {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
}

.background-image {
    width: 100%;
    height: 100%;
    background-image: url("https://i.imgur.com/Qq9V0DG.jpeg");
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    display: none;
}

.show {
    display: block;
}