main {
    background: #aaaaaa;
    padding: 0px;
}

img#intro {
    display: block;
    margin: 100px auto;
    width: min(618px, 90vw);
    height: min(618px, 90vw);
    border-radius: min(309px, 45vw);
}

footer {
    margin-top: 0;
}