:root { --bg:#f5f7fb; --surface:#fff; --surface-alt:#eef2ff; --text:#172033; --muted:#586174; --primary:#4f46e5; --primary-strong:#3730a3; --border:#dce1eb; --success:#047857; --warning:#9a5b06; --shadow:0 16px 45px rgba(27,38,64,.1); --radius:20px; }
[data-theme="dark"] { --bg:#0d1321; --surface:#151d2e; --surface-alt:#1d2945; --text:#eef3ff; --muted:#b4bfd3; --primary:#9ca3ff; --primary-strong:#c7d2fe; --border:#2e3b59; --success:#6ee7b7; --warning:#fcd34d; --shadow:0 16px 45px rgba(0,0,0,.3); }
* { box-sizing:border-box; }
html { scroll-behavior:smooth; }
body { margin:0; color:var(--text); background:radial-gradient(circle at 0 0,rgba(79,70,229,.11),transparent 32rem),var(--bg); font:16px/1.65 Inter,ui-sans-serif,system-ui,-apple-system,"Segoe UI",sans-serif; }
a { color:var(--primary); } button,a.button { font:inherit; } button { border:0; cursor:pointer; }
.skip-link { position:fixed; top:10px; left:10px; z-index:100; padding:9px 14px; border-radius:10px; color:#fff; background:var(--primary); transform:translateY(-160%); }.skip-link:focus { transform:translateY(0); }
.site-shell { width:min(1440px,calc(100% - 32px)); display:grid; grid-template-columns:290px minmax(0,1fr); gap:30px; margin:auto; padding:28px 0 80px; }
.sidebar { position:sticky; top:20px; align-self:start; max-height:calc(100vh - 40px); overflow:auto; padding:20px; border:1px solid var(--border); border-radius:var(--radius); background:color-mix(in srgb,var(--surface) 94%,transparent); box-shadow:var(--shadow); backdrop-filter:blur(12px); }
.brand { display:flex; align-items:center; gap:12px; color:var(--text); text-decoration:none; }.brand:hover { text-decoration:none; }.brand-mark { display:grid; place-items:center; width:44px; height:44px; border-radius:14px; color:#fff; font-weight:900; background:linear-gradient(135deg,var(--primary),#0891b2); }.brand strong,.brand small { display:block; line-height:1.25; }.brand small { margin-top:3px; color:var(--muted); font-size:.78rem; }.sidebar-label { margin:25px 0 8px; color:var(--muted); font-size:.75rem; font-weight:800; letter-spacing:.08em; text-transform:uppercase; }
nav a { display:flex; gap:9px; padding:8px 9px; border-radius:9px; color:var(--text); text-decoration:none; font-size:.88rem; line-height:1.3; } nav a span { flex:0 0 27px; color:var(--primary); font-size:.72rem; font-weight:800; text-align:right; } nav a:hover,nav a:focus-visible,nav a.is-active { color:var(--primary); background:var(--surface-alt); outline:none; }.sidebar-actions { display:grid; gap:9px; margin-top:22px; }
.hero,.learning-section,.intro-card,.stage { border:1px solid var(--border); border-radius:var(--radius); box-shadow:var(--shadow); }.hero { position:relative; overflow:hidden; padding:clamp(34px,6vw,74px); color:#fff; background:linear-gradient(135deg,#4f46e5,#2563eb 52%,#0891b2); }.hero::after { content:""; position:absolute; right:-130px; top:-160px; width:360px; height:360px; border-radius:50%; background:rgba(255,255,255,.12); }.hero>* { position:relative; z-index:1; }.eyebrow { display:inline-block; margin:0; padding:6px 11px; border:1px solid rgba(255,255,255,.28); border-radius:999px; font-size:.82rem; font-weight:750; background:rgba(255,255,255,.14); }.hero h1 { max-width:850px; margin:17px 0; font-size:clamp(2.3rem,6vw,4.7rem); line-height:1.03; letter-spacing:-.045em; }.hero>p:not(.eyebrow) { max-width:760px; margin:0; color:rgba(255,255,255,.9); font-size:1.1rem; }.hero-actions { display:flex; flex-wrap:wrap; gap:10px; margin-top:25px; }
.button { display:inline-flex; align-items:center; justify-content:center; gap:8px; min-height:42px; padding:10px 14px; border:1px solid transparent; border-radius:11px; font-weight:750; text-decoration:none; transition:transform .15s ease,background .15s ease; }.button:hover { transform:translateY(-1px); text-decoration:none; }.button:focus-visible,summary:focus-visible,input:focus-visible { outline:3px solid color-mix(in srgb,var(--primary) 55%,transparent); outline-offset:3px; }.button-primary { color:#fff; background:var(--primary); }.button-primary:hover { background:var(--primary-strong); }.button-secondary { color:var(--text); border-color:var(--border); background:transparent; }.button-secondary:hover { background:var(--surface-alt); }.button-light { color:#1d2540; background:#fff; }.button-outline { color:#fff; border-color:rgba(255,255,255,.42); background:transparent; }
.intro-card,.learning-section { margin-top:30px; padding:clamp(23px,4vw,42px); background:var(--surface); }.intro-card h2,.stage h2 { margin:0 0 8px; font-size:1.32rem; }.stage { margin-top:30px; padding:18px 22px; background:var(--surface-alt); box-shadow:none; }.stage p { margin:0; color:var(--muted); }.section-header { display:flex; gap:15px; align-items:flex-start; margin-bottom:24px; }.section-number { flex:0 0 auto; display:grid; place-items:center; min-width:38px; height:38px; padding:0 7px; border-radius:11px; color:var(--primary); background:var(--surface-alt); font-size:.82rem; font-weight:900; }.section-header h2 { margin:0 0 7px; font-size:clamp(1.6rem,3vw,2.3rem); line-height:1.14; letter-spacing:-.025em; }.section-header p { margin:0; color:var(--muted); }
.two-up,.three-up,.comparison-grid { display:grid; gap:16px; }.two-up,.comparison-grid { grid-template-columns:repeat(2,minmax(0,1fr)); }.three-up { grid-template-columns:repeat(3,minmax(0,1fr)); }.two-up>*,.three-up>*,.comparison-grid>* { padding:18px; border:1px solid var(--border); border-radius:14px; background:color-mix(in srgb,var(--surface) 92%,var(--surface-alt)); }.two-up h3,.three-up h3,.comparison-grid h3 { margin:0 0 7px; font-size:1.03rem; }.two-up p,.three-up p,.comparison-grid p { margin:0; }.two-up ul { margin:0; padding-left:18px; }.two-up li+li { margin-top:5px; }
.lesson-callout,.assignment { margin-top:20px; padding:15px 17px; border-left:4px solid var(--success); border-radius:0 12px 12px 0; background:color-mix(in srgb,var(--success) 9%,var(--surface)); }.lesson-callout.warning { border-color:var(--warning); background:color-mix(in srgb,var(--warning) 11%,var(--surface)); }.assignment { border-color:var(--primary); background:var(--surface-alt); }.key-list,.process-list { margin:0; padding-left:21px; }.key-list li+li,.process-list li+li { margin-top:9px; } details { margin-top:20px; padding:13px 15px; border:1px solid var(--border); border-radius:12px; background:var(--surface-alt); } summary { cursor:pointer; font-weight:800; } details ul { margin-bottom:0; padding-left:20px; }.formula { margin:0 0 18px; padding:12px; border-radius:10px; color:var(--primary); font-weight:850; text-align:center; background:var(--surface-alt); }
.prompt-actions { display:flex; flex-wrap:wrap; align-items:center; gap:10px; margin-top:24px; padding:17px; border:1px dashed color-mix(in srgb,var(--primary) 50%,var(--border)); border-radius:15px; background:color-mix(in srgb,var(--surface-alt) 58%,var(--surface)); }.prompt-actions h3 { flex-basis:100%; margin:0; font-size:1.04rem; }.prompt-actions p { flex-basis:100%; margin:0 0 3px; color:var(--muted); font-size:.9rem; }
.checklist { display:grid; gap:9px; }.checklist label { display:flex; gap:10px; align-items:flex-start; padding:12px 14px; border:1px solid var(--border); border-radius:11px; background:var(--surface-alt); cursor:pointer; }.checklist input { width:18px; height:18px; margin-top:4px; accent-color:var(--primary); }.checklist label:has(input:checked) { color:var(--muted); text-decoration:line-through; }.metric-table { margin-top:20px; overflow-x:auto; border:1px solid var(--border); border-radius:13px; } table { width:100%; border-collapse:collapse; min-width:560px; } caption { padding:13px; font-weight:800; text-align:left; } th,td { padding:12px 14px; border-top:1px solid var(--border); text-align:left; vertical-align:top; } th { background:var(--surface-alt); }.glossary-list { display:grid; grid-template-columns:repeat(2,minmax(0,1fr)); gap:12px; }.glossary-list>div { padding:14px; border:1px solid var(--border); border-radius:12px; background:var(--surface-alt); }.glossary-list dt { color:var(--primary); font-weight:850; }.glossary-list dd { margin:5px 0 0; } footer { padding:30px 10px; color:var(--muted); text-align:center; font-size:.9rem; }.toast { position:fixed; right:20px; bottom:20px; z-index:50; max-width:min(360px,calc(100% - 40px)); padding:12px 15px; border-radius:12px; color:#fff; background:#111827; box-shadow:var(--shadow); opacity:0; pointer-events:none; transform:translateY(14px); transition:.18s ease; }.toast.show { opacity:1; transform:translateY(0); }
.progress-panel { margin-top:22px; padding-top:17px; border-top:1px solid var(--border); }.progress-heading { display:flex; justify-content:space-between; gap:12px; margin-bottom:8px; font-size:.88rem; }.progress-heading strong { color:var(--primary); }#progress-bar { display:block; width:100%; height:8px; accent-color:var(--primary); }#progress-label { display:block; margin-top:7px; color:var(--muted); font-size:.78rem; }
.book-frame { position:relative; margin-top:30px; padding:18px; border:1px solid var(--border); border-radius:24px; background:linear-gradient(135deg,color-mix(in srgb,var(--surface-alt) 76%,var(--surface)),var(--surface)); box-shadow:var(--shadow); scroll-margin-top:20px; }.lesson-book { width:100%; min-height:720px; }.page { min-height:620px; overflow:hidden; background:var(--surface); }.page-stage-label { margin:0; padding:13px 24px 0; color:var(--primary); font-size:.82rem; font-weight:850; letter-spacing:.02em; }.book-frame .learning-section { height:100%; min-height:620px; max-height:100%; margin:0; overflow-y:auto; border:0; border-radius:0; box-shadow:none; }.book-frame .learning-section::-webkit-scrollbar { width:9px; }.book-frame .learning-section::-webkit-scrollbar-thumb { border-radius:99px; background:var(--border); }.lesson-controls { display:grid; gap:15px; margin-top:26px; padding-top:18px; border-top:1px solid var(--border); }.completion-control { display:flex; align-items:center; gap:9px; color:var(--muted); font-size:.9rem; cursor:pointer; }.completion-control input { width:18px; height:18px; accent-color:var(--success); }.page-controls { display:flex; justify-content:space-between; gap:10px; }.page-controls .button:disabled { opacity:.45; cursor:not-allowed; transform:none; }.book-fallback .page { display:none; }.book-fallback .page.is-current { display:block; }.book-fallback .lesson-book { min-height:0; }
.front-cover { width:100%; margin:0 0 30px; transition:opacity .25s ease, max-height .35s ease, margin .35s ease; }.front-cover .hero { width:100%; min-height:620px; }.front-cover[hidden] { display:none !important; }.front-cover.is-dismissed { max-height:0; margin:0; opacity:0; overflow:hidden; }.book-frame { width:min(100%,820px); margin-left:auto; margin-right:auto; }.lesson-book { width:100%; max-width:760px; min-height:920px; margin:0 auto; }.page-preface { padding:32px; overflow:auto; background:var(--surface); }.page-preface .intro-card { margin:0; padding:0; border:0; box-shadow:none; background:transparent; }
.chapter-viewer { width:100%; margin:0 0 30px; scroll-margin-top:20px; }.chapter-card { width:100%; min-height:700px; padding:clamp(23px,4vw,42px); border:1px solid var(--border); border-radius:var(--radius); background:var(--surface); box-shadow:var(--shadow); }.chapter-card > .learning-section,.chapter-card > .intro-card { margin:0; padding:0; border:0; border-radius:0; box-shadow:none; background:transparent; }.chapter-transition { position:fixed; inset:0; z-index:100; display:none; place-items:center; padding:24px; background:color-mix(in srgb,var(--bg) 82%,transparent); }.chapter-transition.is-active { display:grid; }.chapter-transition #transition-book { width:min(100%,960px); height:min(90vh,900px); }.chapter-transition .transition-page { overflow:hidden; background:var(--surface); }.chapter-card .section-header { margin:0 0 26px; padding:26px 0 24px; border-top:0; }.chapter-card .prompt-actions { margin-bottom:0; }.chapter-card .lesson-controls { margin-bottom:0; }.preface-controls { margin-top:30px; }
nav a.is-complete span::after { content:" ✓"; color:var(--success); }
.section-header { display:grid; grid-template-columns:42px minmax(0,1fr); align-items:center; gap:16px; margin:calc(-1 * clamp(23px,4vw,42px)) calc(-1 * clamp(23px,4vw,42px)) 26px; padding:26px clamp(23px,4vw,42px) 24px; border-bottom:1px solid var(--border); background:color-mix(in srgb,var(--surface-alt) 55%,var(--surface)); }
.section-header > .section-number { align-self:center; justify-self:center; }
.section-stage { margin:0 0 5px; color:var(--primary); font-size:.78rem; font-weight:850; letter-spacing:.04em; text-transform:uppercase; }
@media (max-width:720px) { .section-header { grid-template-columns:36px minmax(0,1fr); gap:10px; margin:-22px -22px 22px; padding:20px 22px 19px; }.section-header > .section-number { min-width:36px; height:36px; } }
@media (max-width:1080px) { .site-shell { grid-template-columns:1fr; }.sidebar { position:relative; top:auto; max-height:none; }.sidebar nav { columns:2; }.sidebar-actions { grid-template-columns:repeat(2,minmax(0,1fr)); } }
@media (max-width:720px) { .site-shell { width:min(100% - 20px,1440px); padding-top:10px; }.sidebar nav { columns:1; }.two-up,.comparison-grid,.three-up,.glossary-list { grid-template-columns:1fr; }.hero { border-radius:18px; }.hero h1 { font-size:2.35rem; }.intro-card,.learning-section { padding:22px; }.prompt-actions .button { width:100%; }.sidebar-actions { grid-template-columns:1fr; } }
@media print { body { background:#fff; color:#111; font-size:11pt; }.site-shell { display:block; width:100%; padding:0; }.sidebar,.hero-actions,.prompt-actions,.toast,.skip-link { display:none!important; }.hero,.learning-section,.intro-card,.stage { margin-top:14px; padding:18px; color:#111; background:#fff; box-shadow:none; break-inside:avoid; }.hero::after { display:none; }.hero>p:not(.eyebrow),.section-header p,.stage p { color:#333; }.eyebrow { color:#111; border-color:#999; background:#fff; } }