:root {
  --bg: #f4f7f6;
  --surface: #ffffff;
  --surface-alt: #eef5f2;
  --text: #17211d;
  --muted: #66736d;
  --line: #dce6e1;
  --primary: #176b5b;
  --primary-strong: #0d5144;
  --primary-soft: #dff3ed;
  --accent: #6657d9;
  --accent-soft: #ece9ff;
  --success: #177a4a;
  --success-soft: #e1f6e9;
  --danger: #b43d4a;
  --danger-soft: #fde8ea;
  --warning: #a6690a;
  --warning-soft: #fff1d6;
  --shadow: 0 18px 50px rgba(28, 58, 47, .10);
  --shadow-soft: 0 8px 24px rgba(28, 58, 47, .08);
  --radius: 22px;
  --radius-sm: 14px;
}

[data-theme="dark"] {
  --bg: #101714;
  --surface: #17211d;
  --surface-alt: #1d2a25;
  --text: #f0f6f3;
  --muted: #a7b6af;
  --line: #2b3c35;
  --primary: #56c7aa;
  --primary-strong: #87e1c8;
  --primary-soft: #183b32;
  --accent: #a99cff;
  --accent-soft: #2b2750;
  --success: #67d598;
  --success-soft: #173c29;
  --danger: #ff93a0;
  --danger-soft: #47232a;
  --warning: #ffd072;
  --warning-soft: #433417;
  --shadow: 0 18px 50px rgba(0,0,0,.28);
  --shadow-soft: 0 8px 24px rgba(0,0,0,.22);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
}
button, input { font: inherit; }
button { cursor: pointer; }
button:focus-visible, input:focus-visible, a:focus-visible { outline: 3px solid color-mix(in srgb, var(--accent) 65%, transparent); outline-offset: 3px; }
.hidden { display: none !important; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
.skip-link { position: fixed; z-index: 100; left: 12px; top: -60px; padding: 10px 16px; background: var(--surface); color: var(--text); border-radius: 10px; box-shadow: var(--shadow); }
.skip-link:focus { top: 12px; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 30;
  border-bottom: 1px solid color-mix(in srgb, var(--line) 85%, transparent);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(16px);
}
.header-inner { max-width: 1440px; margin: 0 auto; padding: 14px 28px; display: flex; align-items: center; justify-content: space-between; gap: 20px; }
.brand { display: inline-flex; align-items: center; gap: 12px; color: inherit; text-decoration: none; }
.brand-mark { width: 44px; height: 44px; display: grid; place-items: center; border-radius: 14px; background: linear-gradient(135deg, var(--primary), var(--accent)); color: #fff; font-weight: 800; box-shadow: var(--shadow-soft); }
.brand strong, .brand small { display: block; line-height: 1.2; }
.brand small { margin-top: 4px; color: var(--muted); font-size: .76rem; }
.header-actions { display: flex; align-items: center; gap: 10px; }
.icon-button, .ghost-button, .secondary-button, .primary-button {
  min-height: 44px; border-radius: 12px; border: 1px solid var(--line); padding: 10px 16px; font-weight: 700; transition: transform .18s ease, box-shadow .18s ease, background .18s ease, border-color .18s ease;
}
.icon-button { width: 44px; padding: 0; background: var(--surface); color: var(--text); }
.ghost-button { background: var(--surface); color: var(--text); }
.secondary-button { background: var(--accent-soft); color: var(--accent); border-color: color-mix(in srgb, var(--accent) 35%, var(--line)); }
.primary-button { background: linear-gradient(135deg, var(--primary), var(--primary-strong)); color: #fff; border-color: transparent; box-shadow: 0 10px 22px color-mix(in srgb, var(--primary) 24%, transparent); }
button:hover:not(:disabled) { transform: translateY(-2px); box-shadow: var(--shadow-soft); }
button:disabled { cursor: not-allowed; opacity: .48; }

main { max-width: 1440px; margin: 0 auto; padding: 34px 28px 70px; }
.hero { position: relative; overflow: hidden; min-height: 390px; display: grid; grid-template-columns: 1.25fr .75fr; align-items: center; gap: 40px; padding: 56px; border-radius: 32px; background: linear-gradient(135deg, var(--surface), var(--surface-alt)); border: 1px solid var(--line); box-shadow: var(--shadow); }
.hero::before { content: ""; position: absolute; inset: auto -10% -55% 35%; height: 460px; border-radius: 50%; background: radial-gradient(circle, color-mix(in srgb, var(--primary) 22%, transparent), transparent 68%); }
.hero-copy { position: relative; z-index: 2; max-width: 800px; }
.eyebrow { display: inline-block; color: var(--primary); font-size: .76rem; font-weight: 800; text-transform: uppercase; letter-spacing: .14em; }
h1, h2, h3, h4, p { margin-top: 0; }
h1 { font-size: clamp(2.1rem, 5vw, 4.4rem); line-height: 1.06; letter-spacing: -.045em; margin-bottom: 22px; }
.hero p { max-width: 720px; color: var(--muted); font-size: 1.05rem; }
.hero-stats { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 30px; }
.stat-chip { min-width: 130px; padding: 13px 16px; border-radius: 14px; background: color-mix(in srgb, var(--surface) 78%, transparent); border: 1px solid var(--line); }
.stat-chip strong { display: block; font-size: 1.35rem; line-height: 1.2; }
.stat-chip span { color: var(--muted); font-size: .78rem; }
.hero-visual { position: relative; z-index: 2; min-height: 280px; display: grid; place-items: center; }
.cell { position: absolute; border-radius: 50%; border: 3px solid color-mix(in srgb, var(--primary) 32%, transparent); background: radial-gradient(circle at 35% 35%, color-mix(in srgb, var(--primary) 35%, transparent), color-mix(in srgb, var(--accent) 12%, transparent)); box-shadow: inset 0 0 30px color-mix(in srgb, var(--primary) 18%, transparent); }
.cell::before, .cell::after { content:""; position:absolute; border-radius:50%; background: color-mix(in srgb, var(--accent) 40%, transparent); }
.cell-a { width: 230px; height: 230px; right: 4%; top: 6%; animation: float 7s ease-in-out infinite; }
.cell-a::before { width: 62px; height: 62px; left: 78px; top: 72px; }
.cell-a::after { width: 20px; height: 20px; right: 35px; bottom: 46px; }
.cell-b { width: 105px; height: 105px; left: 6%; bottom: 2%; animation: float 5.5s ease-in-out infinite reverse; }
.cell-b::before { width: 28px; height: 28px; left: 36px; top: 32px; }
.dna { position: relative; transform: rotate(-8deg); padding: 18px 22px; border-radius: 28px; color: var(--accent); font-weight: 800; letter-spacing: .7em; line-height: 1.05; background: color-mix(in srgb, var(--surface) 72%, transparent); border: 1px solid var(--line); box-shadow: var(--shadow); }
@keyframes float { 50% { transform: translateY(-14px) rotate(4deg); } }

.library { margin-top: 56px; }
.section-heading { display: flex; align-items: end; justify-content: space-between; gap: 24px; margin-bottom: 24px; }
.section-heading h2 { margin: 5px 0 0; font-size: clamp(1.65rem, 3vw, 2.4rem); letter-spacing: -.03em; }
.filter-group { display: flex; gap: 8px; padding: 5px; border-radius: 14px; background: var(--surface); border: 1px solid var(--line); }
.filter-button { border: 0; border-radius: 10px; padding: 9px 14px; color: var(--muted); background: transparent; font-weight: 700; }
.filter-button.active { color: #fff; background: var(--primary); }
.quick-start { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); gap: 18px; margin-bottom: 22px; }
.aggregate-card { display: flex; align-items: center; justify-content: space-between; gap: 18px; padding: 22px; border: 1px solid var(--line); border-radius: var(--radius); background: linear-gradient(135deg, var(--surface), var(--primary-soft)); box-shadow: var(--shadow-soft); }
.aggregate-card h3 { margin: 4px 0; }
.aggregate-card p { margin: 0; color: var(--muted); }
.section-grid { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 18px; }
.section-card { position: relative; overflow: hidden; display: flex; flex-direction: column; min-height: 225px; padding: 24px; border-radius: var(--radius); border: 1px solid var(--line); background: var(--surface); box-shadow: var(--shadow-soft); transition: transform .2s ease, box-shadow .2s ease, border-color .2s ease; }
.section-card:hover { transform: translateY(-5px); box-shadow: var(--shadow); border-color: color-mix(in srgb, var(--primary) 40%, var(--line)); }
.section-card::after { content:""; position:absolute; width:130px; height:130px; border-radius:50%; right:-56px; bottom:-70px; background: color-mix(in srgb, var(--primary) 9%, transparent); }
.section-card h3 { margin: 10px 0 12px; font-size: 1.05rem; line-height: 1.45; }
.section-card p { color: var(--muted); font-size: .88rem; }
.section-card footer { margin-top: auto; display: flex; align-items: center; justify-content: space-between; gap: 12px; }
.count-pill { padding: 6px 10px; border-radius: 999px; background: var(--surface-alt); color: var(--muted); font-size: .76rem; font-weight: 700; }
.start-button { border: 0; background: transparent; color: var(--primary); font-weight: 800; padding: 8px; }

.quiz-shell { display: grid; grid-template-columns: 300px minmax(0,1fr); gap: 28px; align-items: start; }
.quiz-sidebar { position: sticky; top: 94px; display: grid; gap: 16px; max-height: calc(100vh - 115px); overflow: auto; padding-right: 4px; }
.sidebar-card { padding: 20px; border-radius: var(--radius-sm); background: var(--surface); border: 1px solid var(--line); box-shadow: var(--shadow-soft); }
.sidebar-card h2 { margin: 6px 0 8px; font-size: 1rem; line-height: 1.45; }
.sidebar-card p { margin: 0; color: var(--muted); font-size: .83rem; }
.progress-label { display: flex; justify-content: space-between; font-size: .82rem; }
.progress-track { height: 9px; margin: 12px 0 16px; border-radius: 999px; overflow: hidden; background: var(--surface-alt); }
.progress-track span { display: block; width: 0; height: 100%; border-radius: inherit; background: linear-gradient(90deg,var(--primary),var(--accent)); transition: width .3s ease; }
.mini-stats { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.mini-stats div { padding: 10px; border-radius: 12px; background: var(--surface-alt); }
.mini-stats strong, .mini-stats span { display: block; }
.mini-stats strong { font-size: 1.15rem; }
.mini-stats span { color: var(--muted); font-size: .7rem; }
.question-nav { display: grid; grid-template-columns: repeat(5,1fr); gap: 7px; padding: 14px; border: 1px solid var(--line); border-radius: var(--radius-sm); background: var(--surface); }
.qnav-button { aspect-ratio: 1; border: 1px solid var(--line); border-radius: 9px; background: var(--surface-alt); color: var(--muted); font-size: .73rem; font-weight: 800; }
.qnav-button.current { color: #fff; background: var(--primary); border-color: var(--primary); }
.qnav-button.done { color: var(--success); background: var(--success-soft); border-color: color-mix(in srgb, var(--success) 35%, var(--line)); }
.qnav-button.wrong { color: var(--danger); background: var(--danger-soft); border-color: color-mix(in srgb, var(--danger) 35%, var(--line)); }
.quiz-main { min-width: 0; }
.quiz-toolbar { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 14px; color: var(--muted); font-size: .86rem; }
.question-card { padding: clamp(22px,4vw,44px); border: 1px solid var(--line); border-radius: 28px; background: var(--surface); box-shadow: var(--shadow); }
.question-header { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 24px; }
.question-number { padding: 7px 12px; border-radius: 999px; background: var(--primary-soft); color: var(--primary); font-size: .8rem; font-weight: 800; }
.multi-badge { padding: 7px 12px; border-radius: 999px; background: var(--warning-soft); color: var(--warning); font-size: .76rem; font-weight: 800; }
.question-statement { margin: 0 0 26px; font-size: clamp(1.18rem,2.2vw,1.58rem); line-height: 1.55; letter-spacing: -.015em; }
.context-box { margin-bottom: 24px; padding: 18px 20px; border-radius: var(--radius-sm); background: var(--surface-alt); border-left: 4px solid var(--primary); }
.context-box strong { display: block; margin-bottom: 5px; color: var(--primary); }
.context-box p { margin: 0; color: var(--muted); }
.source-panel { margin: 0 0 26px; padding: 18px; border: 1px solid var(--line); border-radius: var(--radius-sm); background: var(--surface-alt); }
.source-heading { display: flex; align-items: center; justify-content: space-between; gap: 14px; }
.source-heading h4 { margin: 3px 0 0; }
.source-pages { display: grid; gap: 14px; margin-top: 18px; }
.source-page { position: relative; overflow: hidden; border-radius: 12px; background: #fff; border: 1px solid var(--line); }
.source-page img { display: block; width: 100%; height: auto; cursor: zoom-in; }
.source-page span { position: absolute; top: 10px; left: 10px; padding: 5px 9px; border-radius: 8px; background: rgba(10,20,16,.76); color: #fff; font-size: .7rem; font-weight: 700; }
.answers-list { display: grid; gap: 12px; }
.answer-option { position: relative; display: grid; grid-template-columns: 42px minmax(0,1fr); align-items: center; gap: 14px; width: 100%; padding: 15px 18px; border: 1px solid var(--line); border-radius: 15px; background: var(--surface); color: var(--text); text-align: left; transition: border-color .18s, background .18s, transform .18s; }
.answer-option:hover:not(:disabled) { border-color: var(--primary); background: var(--primary-soft); transform: translateX(3px); }
.answer-letter { width: 36px; height: 36px; display: grid; place-items: center; border-radius: 10px; background: var(--surface-alt); color: var(--primary); font-weight: 800; border: 1px solid var(--line); }
.answer-option.selected { border-color: var(--accent); background: var(--accent-soft); }
.answer-option.selected .answer-letter { background: var(--accent); color: #fff; border-color: var(--accent); }
.answer-option.correct { border-color: var(--success); background: var(--success-soft); }
.answer-option.correct .answer-letter { background: var(--success); color: #fff; border-color: var(--success); }
.answer-option.incorrect { border-color: var(--danger); background: var(--danger-soft); }
.answer-option.incorrect .answer-letter { background: var(--danger); color: #fff; border-color: var(--danger); }
.feedback { margin-top: 20px; padding: 16px 18px; border-radius: 14px; font-weight: 700; }
.feedback.success { color: var(--success); background: var(--success-soft); }
.feedback.error { color: var(--danger); background: var(--danger-soft); }
.question-actions { display: flex; align-items: center; gap: 12px; margin-top: 28px; padding-top: 22px; border-top: 1px solid var(--line); }
.action-spacer { flex: 1; }
.mobile-only { display: none; }

.results-card { max-width: 820px; margin: 10px auto 50px; padding: 48px; text-align: center; border-radius: 30px; border: 1px solid var(--line); background: var(--surface); box-shadow: var(--shadow); }
.results-card h1 { font-size: clamp(2rem,5vw,3.5rem); }
.score-ring { width: 190px; height: 190px; margin: 28px auto; display: grid; place-content: center; border-radius: 50%; background: radial-gradient(circle at center,var(--surface) 58%,transparent 59%), conic-gradient(var(--primary) var(--score-angle,0deg),var(--surface-alt) 0); box-shadow: inset 0 0 0 1px var(--line); }
.score-ring strong { display: block; font-size: 2rem; }
.score-ring span { color: var(--muted); }
.result-message { color: var(--muted); font-size: 1.05rem; }
.result-stats { display: grid; grid-template-columns: repeat(3,1fr); gap: 12px; margin: 26px 0; }
.result-stat { padding: 16px; border-radius: 14px; background: var(--surface-alt); }
.result-stat strong, .result-stat span { display: block; }
.result-stat strong { font-size: 1.35rem; }
.result-stat span { color: var(--muted); font-size: .78rem; }
.result-actions { display: flex; flex-wrap: wrap; justify-content: center; gap: 10px; }
.review-section { max-width: 980px; margin: 0 auto; }
.review-list { display: grid; gap: 16px; }
.review-card { padding: 22px; border: 1px solid var(--line); border-radius: var(--radius-sm); background: var(--surface); box-shadow: var(--shadow-soft); }
.review-card h3 { font-size: 1rem; }
.review-answer { display: flex; flex-wrap: wrap; gap: 10px; color: var(--muted); font-size: .84rem; }
.review-answer strong { color: var(--text); }
.image-dialog { width: min(96vw,1100px); max-height: 94vh; padding: 0; border: 0; border-radius: 18px; background: transparent; box-shadow: var(--shadow); }
.image-dialog::backdrop { background: rgba(5,12,9,.8); backdrop-filter: blur(6px); }
.image-dialog img { display: block; width: 100%; height: auto; max-height: 94vh; object-fit: contain; background: #fff; }
.dialog-close { position: fixed; top: 18px; right: 22px; z-index: 3; width: 46px; height: 46px; border-radius: 50%; border: 0; background: rgba(0,0,0,.72); color: #fff; font-size: 1.7rem; }
.site-footer { padding: 28px; color: var(--muted); text-align: center; font-size: .8rem; }

@media (max-width: 1050px) {
  .section-grid { grid-template-columns: repeat(2,minmax(0,1fr)); }
  .quiz-shell { grid-template-columns: 250px minmax(0,1fr); gap: 18px; }
  .hero { grid-template-columns: 1fr; }
  .hero-visual { display: none; }
}
@media (max-width: 760px) {
  .header-inner, main { padding-left: 16px; padding-right: 16px; }
  .brand small { display: none; }
  .hero { min-height: auto; padding: 34px 24px; border-radius: 24px; }
  h1 { font-size: 2.25rem; }
  .section-heading { align-items: stretch; flex-direction: column; }
  .filter-group { width: 100%; }
  .filter-button { flex: 1; }
  .quick-start, .section-grid { grid-template-columns: 1fr; }
  .aggregate-card { align-items: flex-start; flex-direction: column; }
  .quiz-shell { display: block; }
  .quiz-sidebar { display: none; position: fixed; z-index: 50; inset: 80px 14px 14px; max-height: none; padding: 16px; border-radius: 20px; background: var(--bg); box-shadow: var(--shadow); }
  .quiz-sidebar.open { display: grid; }
  .mobile-only { display: inline-flex; }
  .question-card { padding: 22px 17px; border-radius: 22px; }
  .question-toolbar { flex-wrap: wrap; }
  .answer-option { grid-template-columns: 38px minmax(0,1fr); padding: 13px; }
  .question-actions { flex-wrap: wrap; }
  .action-spacer { display: none; }
  .question-actions button { flex: 1; min-width: 145px; }
  .results-card { padding: 34px 20px; }
  .result-stats { grid-template-columns: 1fr; }
}
@media print {
  .site-header, .site-footer, .quiz-sidebar, .quiz-toolbar, .question-actions, .source-heading button { display: none !important; }
  body, main { background: #fff; padding: 0; }
  .question-card { box-shadow: none; border: 0; padding: 0; }
  .source-pages { display: grid !important; }
  .answer-option { break-inside: avoid; }
}