body {
    margin: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    position: relative;
}

#space {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translateX(-50%) translateY(-50%);
    white-space: pre-line;
    width: 500px;
}

#space > span {
    line-height: 200%;
}

#video {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translateX(-50%) translateY(-50%);
    z-index: -1;
    display: none;
}

#switch {
    position: fixed;
    left: 50%;
    bottom: 5%;
    transform: translateX(-50%);
}

.fadein {
    animation: fadein 3s ease;
}

@keyframes fadein {
    0% {
        opacity: 0;
    }
    100% {
        opacity: 1;
    }
}

a {
    color: gray;
    text-decoration: none;
}