body {
    display: flex; flex-direction: column;
    align-items: center;
}

#introh1 { width: fit-content; text-align: center; }
#introlabel { width: fit-content; text-align: center; }

#content {
    position: fixed; transform: translate(-50%, -50%);
    top: 50%; left: 50%; display: flex;
    flex-direction: column; align-items: center;
}