html, body {
    width: 100%; height: 100%;
    margin: 0; padding: 0;
}
#split-screen {
    display: flex;
    flex-direction: row;
    align-content: stretch;
}
iframe {
    flex-grow: 1;
}
#diff {
    white-space: pre-wrap;
    color: gray;
}
.add {
    color: green;
}
.remove {
    color: red;
    text-decoration: line-through;
}