style.css

body {
    margin: 5ex 10ex;
    max-width: 80ex;
    line-height: 1.5;
    font-family: sans-serif;
}
h1, h2, h3 {
    font-weight: normal;
}
pre, code {
    font-family: x, monospace;
}
pre {
    padding: 1ex;
    background: #eee;
    border: solid 1px #ddd;
    min-width: 0;
    font-size: 90%;
}
code {
    color: #007;
}
div.chapter {
    margin-top: 4em;
    border-top: solid 2px black;
}
p {
    margin-top: 0;
}