body {
    margin: 0;
    padding: 0;
    position: relative;
    width: 100%;
    height: 100vh;
}

.background-image {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: url(../img/moc-comingsoon-pc.png);
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    opacity: 0;
    transition: opacity 2s ease-in-out;
}

@media (max-width: 768px) {
    .background-image {
        background-image: url(../img/moc-comingsoon-sp.png);
    }
}

.background-image.fade-in {
    opacity: 1;
}