help.css

html {
    font-size: 18px;
}

body {
    font-family: sans-serif;
}

header {
    text-align: center;
}

main {
    max-width: 40rem;
    margin: 0 auto;
}

footer {
    margin-top: 3em;
    font-style: italic;
}
th {
    text-align: left;
}
th, td {
    padding: 0.5em;
}

td p {
    margin-top: 0;
}
td:first-child {
    white-space: nowrap;
}

tr ~ tr td {
    border-top: 1px dashed black;
}
kbd {
    background: #ddd;
    padding: 0.2em 0.5em;
    border-radius: 0.2em;
    margin: 0.1em 0;
    display: inline-block;
}