.p6-box, footer {
    margin: 1em;
    padding: 1em;
    border-radius: 20px;
}

article.p6-book {
    border: 2px solid blue;
}
section.intro {
    border: 2px solid green;
    max-width: 80.3em;
}

.p6-book-properties th {
    text-align: right;
}

th, tr {
    padding: 2px;
}
th {
    padding-right: 1ex;
}

.p6-books-container {
    display: flex;
    flex-wrap: wrap;
}
.p6-book {
    width: 24em;
}

.p6-unavailable {
    background-color: #eee;
}

footer {
    background-color: #ddd;
}