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

.full-screen-bg {
    background-image: url('https://petter-riise.net/IMG88888.jpg');
    background-size: cover;
    background-position: center;
    position: relative;
    width: 100%;
    height: 100%;
}