/* Learning navigation: one clear action at each step, colour with purpose. */
:root {--brand:#3157bd;--brand-d:#244393;--brand-l:#edf1ff;--bg:#f5f7fc;--line:#dbe2ef}
:root[data-theme="dark"] {--brand:#aabfff;--brand-d:#c0ceff;--brand-l:#273451;--bg:#151b26;--line:#3c495e}
@media(prefers-color-scheme:invalid){:root:not([data-theme="light"]){--brand:#aabfff;--brand-d:#c0ceff;--brand-l:#273451;--bg:#151b26;--line:#3c495e}}
.btn.primary,.hero .btn.primary {background:#3157bd;border-color:#3157bd}
.btn {border-radius:10px}
.btn.ghost {background:var(--surface)}
.hero {background:linear-gradient(120deg,var(--surface),var(--brand-l));border-bottom:1px solid var(--line)}
.hero-cta .btn {font-size:16px;padding:12px 16px}
.gcard {border-top:3px solid color-mix(in srgb,var(--gc) 60%,var(--line))}
.gnum {background:var(--brand-l);color:var(--brand)}
.gbadge.live {background:var(--ok-l);color:var(--ok-d)}
.topnav {align-items:center;gap:4px}
.topnav>a {white-space:nowrap}
.header-more {position:relative;font-size:15px;flex:none}
.header-more summary {cursor:pointer;padding:10px 14px;min-height:44px;color:var(--ink-2);border-radius:8px;font-weight:600}
.header-more[open] summary {background:var(--brand-l);color:var(--brand)}
.header-more nav {position:absolute;right:0;top:100%;z-index:50;min-width:230px;padding:8px;background:var(--surface);border:1px solid var(--line);border-radius:10px;box-shadow:0 8px 24px #14234418}
.header-more nav a {display:block;padding:12px;white-space:normal}
.abi-course-page {max-width:1000px;padding-top:18px}
.abi-breadcrumb {font-size:14px;color:var(--ink-2);margin:0 0 16px}
.abi-text-link {color:var(--brand);text-underline-offset:3px}
.abi-course-nav {display:flex;gap:6px;margin-bottom:24px;border-bottom:1px solid var(--line)}
.abi-course-nav a {padding:12px 20px;border-bottom:3px solid transparent;color:var(--ink-2);text-decoration:none;font-weight:700;min-height:48px}
.abi-course-nav a[aria-current=page] {color:var(--brand);border-bottom-color:var(--brand)}
.abi-course-page h1 {font-size:clamp(25px,4vw,34px)}
.abi-course-page .lead {color:var(--ink-2);max-width:65ch}
.abi-learning-hint {background:var(--brand-l);color:var(--brand-d);border-radius:10px;padding:14px 18px}
.abi-course-list {display:grid;gap:10px}
.abi-course-row {display:grid;grid-template-columns:44px minmax(0,1fr) 20px;gap:16px;align-items:center;padding:16px;background:var(--surface);border:1px solid var(--line);border-radius:12px;text-decoration:none;color:var(--ink)}
.abi-course-row:hover {border-color:var(--brand);background:color-mix(in srgb,var(--brand-l) 28%,var(--surface))}
.abi-course-number {display:grid;place-items:center;min-height:44px;border-radius:10px;background:var(--brand-l);color:var(--brand);font-size:17px;font-weight:750}
.abi-course-row small {display:block;font-size:12px;color:var(--muted)}
.abi-course-row strong {display:block;font-size:18px;line-height:1.45}
.abi-course-status {display:block;font-size:13px;color:var(--ink-2);margin-top:4px}
.abi-course-tabs {display:flex;flex-wrap:wrap;gap:4px;background:var(--surface-2);border-radius:10px;padding:4px;margin:18px 0}
.abi-course-tabs a {padding:10px 18px;border-radius:8px;font-weight:700;text-decoration:none;color:var(--ink-2);min-height:44px}
.abi-course-tabs a[aria-current=page] {background:var(--surface);color:var(--brand);box-shadow:0 1px 3px #0001}
.abi-section-title {margin:28px 0 14px}
.abi-school-section h2 {font-size:23px}
.abi-school-section .card-body {padding:0;min-width:0}
.abi-school-section .tip-m {display:none}
.abi-school-section .rule {border-width:1px;background:var(--brand-l)}
.abi-next-step {border-inline-start:4px solid var(--brand)}
.abi-source-links {padding:16px 0;color:var(--ink-2)}
.abi-source-links summary {cursor:pointer;min-height:44px}
.abi-rule-row {padding:12px 0;border-top:1px solid var(--line)}
.abi-book-option {border:1px solid var(--line);min-height:56px;border-radius:10px}
.abi-book-option>strong {display:grid;place-items:center;flex:none;width:28px;height:28px;border-radius:6px;background:var(--surface-2);font-size:14px}
.abi-book-option[aria-pressed=true] {outline:2px solid var(--brand);outline-offset:-2px;background:var(--brand-l)}
.abi-book-option[aria-pressed=true]>strong {background:#3157bd;color:white}
.abi-book-option:disabled {cursor:default;color:var(--ink)}
.abi-text-button {min-height:44px;padding:8px 4px;border:0;background:transparent;color:var(--brand);font:700 16px var(--font);text-decoration:underline;text-underline-offset:4px;cursor:pointer}
.abi-exam-grid {display:grid;grid-template-columns:repeat(auto-fill,minmax(130px,1fr));gap:12px;margin:24px 0}
.abi-exam-link {display:block;padding:18px;text-decoration:none;border:1px solid var(--line);background:var(--surface);border-radius:10px;color:var(--brand);font-weight:700}
.abi-school-section .eqline {max-width:100%;overflow-x:auto}
.abi-school-section .cols {min-width:0;max-width:100%}
@media(max-width:900px){
 .topbar-in {flex-wrap:wrap;padding-block:8px;gap:8px}
 .topnav,body.zoom-tablet .topnav {display:flex;order:3;width:100%;margin-left:0;overflow:visible;flex-wrap:wrap;justify-content:space-between}
 .topnav>a,.header-more summary {padding:9px 10px;font-size:14px;min-height:44px}
 .topstats .pill {display:none}
}
@media(max-width:520px){
 .abi-course-nav {gap:0}
 .abi-course-nav a {flex:1;text-align:center;padding:11px 8px}
 .abi-course-row {grid-template-columns:36px minmax(0,1fr) 14px;padding:12px;gap:10px}
 .abi-course-number {font-size:15px;min-height:38px}
 .abi-course-row strong {font-size:17px}
 .abi-course-tabs a {padding:10px 12px}
 .abi-school-section h2 {font-size:21px}
}
@media print{.abi-course-nav,.abi-course-tabs,.abi-breadcrumb,.abi-source-links{display:none}}

/* Long mathematics scrolls inside its own panel, never the page. */
.abi-school-section .math-panel {width:100%;box-sizing:border-box}
.abi-school-section .math-scroll {max-width:100%;overflow-x:auto}
.header-more nav {min-width:0;width:230px;max-width:calc(var(--zoom-view-width, 100vw) - 32px)}
body.zoom-small .abi-course-nav {flex-wrap:wrap}
body.zoom-small .abi-course-nav a {padding:10px 8px}
body.zoom-small .abi-course-row {grid-template-columns:30px minmax(0,1fr);gap:8px}
body.zoom-small .abi-course-row>span:last-child {display:none}

body.zoom-tablet .topnav {display:flex;flex-wrap:wrap;order:3;width:100%;margin-left:0;justify-content:space-between;overflow:visible}
body.zoom-small .abi-course-nav {flex-direction:column;align-items:stretch}
body.zoom-small .abi-filters {display:flex;flex-direction:column;align-items:stretch}
body.zoom-small .abi-course-tabs a {padding:8px;font-size:14px}