/* Edexcel companions: the existing black-and-gold resource palette. */
.textbook-page .textbook-hero{background:#111;color:#f7f5f0;padding:28px 0 32px;border-bottom:3px solid #b69250}
.textbook-page .textbook-hero h1{font:700 clamp(2rem,4.5vw,3.5rem)/1.12 Georgia,serif;letter-spacing:-.02em;color:#fff;margin:16px 0;max-width:930px}
.textbook-page .textbook-hero p{color:#eee8dc;max-width:800px;font-size:1.06rem}
.textbook-page .textbook-hero .topic-kicker,.textbook-page .textbook-hero a{color:#ead9b6}
.textbook-page .textbook-hero .topic-jumps a{background:#ead9b6;color:#211b11}
.textbook-page .textbook-breadcrumbs{display:flex;flex-wrap:wrap;gap:9px;font-size:.9rem}
.textbook-page .textbook-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:20px;margin:28px 0 36px}
.textbook-page .book-card{display:flex;flex-direction:column;min-width:0;background:#fff;color:#28231b;border:1px solid #d9d0c0;border-radius:10px;overflow:hidden}
.textbook-page .book-card-top{padding:24px 24px 18px;background:#1b1b1b;border-top:4px solid #b69250;color:#ead9b6}
.textbook-page .book-card-top h2{font:700 1.65rem/1.2 Georgia,serif;margin:8px 0 0;color:#fff}
.textbook-page .book-card-top a{color:inherit;text-decoration:none}
.textbook-page .book-card-body{padding:22px;display:flex;flex-direction:column;flex:1}
.textbook-page .book-card-body p{margin:0 0 18px;color:#493f30}
.textbook-page .book-card-body .resource-button{margin-top:auto;align-self:flex-start;background:#ead9b6;color:#211b11!important;border:1px solid #b69250}
.textbook-page .book-card-body .resource-button:hover,.textbook-page .book-card-body .resource-button:focus-visible{background:#72531c;color:#fff!important}
.textbook-page .textbook-section{padding:28px 0;scroll-margin-top:100px}
.textbook-page .textbook-section>h2{font:700 1.9rem/1.2 Georgia,serif;margin:0 0 12px;color:#1c1c1c}
.textbook-page .textbook-note{background:#eee8dc;color:#393329;border-left:4px solid #8a6526;padding:18px 22px;margin:24px 0}
.textbook-page .textbook-note p{margin:5px 0}
.textbook-page .chapter-layout{display:grid;grid-template-columns:230px minmax(0,1fr);gap:28px;align-items:start}
.textbook-page .chapter-menu{background:#fff;border:1px solid #d9d0c0;border-radius:8px;padding:16px;position:sticky;top:85px;max-height:75vh;overflow:auto}
.textbook-page .chapter-menu h3{margin:0 0 10px;font-size:1rem}
.textbook-page .chapter-menu a{display:block;padding:9px 0;font-size:.9rem;line-height:1.35;color:#634614;border-bottom:1px solid #eee8dc;text-decoration:none}
.textbook-page .chapter-list{min-width:0}
.textbook-page .chapter{background:#fff;border:1px solid #d9d0c0;border-radius:8px;margin-bottom:14px;scroll-margin-top:100px;overflow:hidden}
.textbook-page .chapter summary{padding:18px 20px;cursor:pointer;font-weight:700;font-size:1.08rem;color:#28231b}
.textbook-page .chapter summary::marker{color:#72531c}
.textbook-page .chapter[open] summary{background:#eee8dc;border-bottom:1px solid #d9d0c0}
.textbook-page .chapter-content{padding:18px 20px;color:#393329}
.textbook-page .chapter-content>p{margin:0 0 14px}
.textbook-page .exercise-links{display:flex;flex-wrap:wrap;gap:9px}
.textbook-page .exercise-links a{display:inline-flex;align-items:center;min-height:44px;padding:8px 13px;border:1px solid #cbb894;border-radius:5px;color:#634614;background:#fff;font-size:.94rem;text-decoration:none;font-weight:650}
.textbook-page .exercise-links a.mixed{background:#ead9b6;color:#211b11;border-color:#b69250}
.textbook-page .practice-route{font-size:.93rem;border-left:3px solid #b69250;padding-left:12px;margin-top:17px!important}
.textbook-page .practice-route a{color:#634614;font-weight:650}
.textbook-page .practice-card{margin:22px 0;border:1px solid #d9d0c0;border-radius:8px;background:#fff;color:#28231b;overflow:hidden}
.textbook-page .practice-head{background:#111;color:#fff;padding:20px 24px;border-top:3px solid #b69250}
.textbook-page .practice-head h3{margin:0 0 12px;color:#ead9b6;font-size:1.12rem}
.textbook-page .practice-head p{margin:6px 0}
.textbook-page .practice-body{padding:14px 22px 22px}
.textbook-page .practice-body details{border:1px solid #d9d0c0;margin-top:9px;border-radius:5px;color:#28231b}
.textbook-page .practice-body summary{padding:12px 15px;color:#634614;cursor:pointer;font-weight:700}
.textbook-page .practice-body details>div{padding:0 15px 12px}
.textbook-page .practice-body details>div p{margin:8px 0}
.textbook-page .download-row{display:flex;gap:10px;flex-wrap:wrap;margin:20px 0}
.textbook-page .download-row a{background:#ead9b6;color:#211b11;border:1px solid #b69250;padding:10px 15px;border-radius:5px;font-weight:700;text-decoration:none;min-height:44px}
.textbook-page .book-switcher{display:flex;gap:8px;flex-wrap:wrap;margin:20px 0}
.textbook-page .book-switcher a{padding:9px 12px;border:1px solid #cbb894;border-radius:5px;background:#fff;color:#634614;font-size:.92rem;text-decoration:none}
.textbook-page .book-switcher a[aria-current]{background:#111;color:#ead9b6;border-color:#111}
.textbook-page .textbook-credit{font-size:.9rem;color:#5d564b;max-width:960px;margin:24px 0}
.textbook-page .textbook-credit a{color:#634614}
.textbook-page .katex{font-size:1.08em}.textbook-page .katex-display{overflow-x:auto;overflow-y:hidden;padding:4px 0;max-width:100%}
.textbook-page math[display="block"]{display:block;overflow-x:auto;padding:8px 0;max-width:100%}
.textbook-page .textbook-hero :focus-visible{outline-color:#ead9b6}
@media(max-width:1000px){.textbook-page .textbook-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.textbook-page .chapter-layout{grid-template-columns:190px minmax(0,1fr);gap:20px}}
@media(max-width:700px){.textbook-page .textbook-grid{grid-template-columns:minmax(0,1fr)}.textbook-page .chapter-layout{display:block}.textbook-page .chapter-menu{position:static;max-height:none;margin-bottom:20px}.textbook-page .chapter-menu nav{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:0 14px}.textbook-page .practice-head{padding:18px}.textbook-page .practice-body{padding:12px 16px 16px}}
@media print{.textbook-page .site-header,.textbook-page .paper-archive-bar,.textbook-page .chapter-menu,.textbook-page .topic-tuition,.textbook-page footer,.textbook-page .book-switcher,.textbook-page .download-row{display:none}.textbook-page .textbook-hero,.textbook-page .practice-head{background:#fff;color:#111}.textbook-page .textbook-hero h1,.textbook-page .textbook-hero p,.textbook-page .practice-head h3{color:#111}.textbook-page .chapter-layout{display:block}.textbook-page .practice-card{break-inside:avoid}}
@media print{.textbook-page .textbook-hero .topic-kicker,.textbook-page .textbook-hero a,.textbook-page .book-card-top,.textbook-page .book-card-top h2,.textbook-page .book-card-top a{background:#fff;color:#111}.textbook-page .book-card-body .resource-button{background:#fff;color:#111!important}}