.textbook-page {
    max-width: 960px;
    margin: 0 auto;
    padding: 0 16px;
}

.textbook-page h1 {
    line-height: 1.25;
}

.textbook-page .intro {
    color: #555;
    max-width: 70ch;
}

.breadcrumb {
    font-size: 0.85em;
    color: #777;
}

.plan-cta {
    display: inline-block;
    background: #6153cc;
    color: #fff;
    padding: 10px 20px;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    margin: 6px 0 18px;
}

.plan-cta:hover {
    background: #4f42b5;
}

.plan-cta.small {
    padding: 6px 14px;
    font-size: 0.9em;
}

.edition-note {
    color: #777;
    font-size: 0.88em;
    max-width: 80ch;
}

.chapter-table {
    border-collapse: collapse;
    width: 100%;
    margin: 10px 0 24px;
}

.chapter-table th {
    text-align: left;
    font-size: 0.78em;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: #777;
    border-bottom: 2px solid #ddd;
    padding: 6px 10px;
}

.chapter-table td {
    border-bottom: 1px solid #e8e8e8;
    padding: 9px 10px;
    vertical-align: top;
}

.ch-num {
    font-weight: 700;
    color: #6153cc;
    white-space: nowrap;
    width: 2.5em;
}

.ch-title {
    width: 38%;
    min-width: 170px;
}

.topic-links {
    margin: 0;
    padding-left: 18px;
}

.topic-links li {
    margin: 2px 0;
}

.topic-links .pdf {
    color: #777;
    font-size: 0.9em;
}

tr.gap .ch-title,
tr.gap .ch-num {
    color: #999;
}

.no-practice {
    color: #999;
    font-size: 0.9em;
    font-style: italic;
}

.older-edition {
    border: 1px solid #e2e0ef;
    border-radius: 8px;
    padding: 4px 16px;
    margin: 14px 0;
    background: #fafafa;
}

.older-edition summary {
    cursor: pointer;
    font-weight: 600;
    padding: 8px 0;
    color: #4f42b5;
}

.feedback-note {
    color: #666;
    font-size: 0.9em;
    border-top: 1px solid #eee;
    padding-top: 14px;
    margin-top: 24px;
}

.book-columns {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 0 32px;
}

.book-list {
    list-style: none;
    padding: 0;
}

.book-list li {
    margin: 10px 0;
}

.book-list .topic-desc {
    display: block;
    color: #777;
    font-size: 0.85em;
}