:root {
  --ink: #10232d;
  --muted: #5b6c74;
  --paper: #f4f1e9;
  --panel: #fffdf8;
  --deep: #0b2533;
  --teal: #0d7c78;
  --teal-light: #8ad5c7;
  --amber: #ee9e2d;
  --red: #b9423c;
  --line: #d7d4ca;
  --shadow: 0 18px 50px rgba(11, 37, 51, .10);
}

* { box-sizing: border-box; }
body { margin: 0; background: var(--paper); color: var(--ink); font-family: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; line-height: 1.5; }
button, input, select { font: inherit; }
button { cursor: pointer; }
a { color: var(--teal); font-weight: 700; }
.institution-bar { min-height: 58px; display: flex; align-items: center; gap: 18px; padding: 11px clamp(20px, 4vw, 64px); background: white; border-bottom: 1px solid #cbd1d6; }
.institution-brand { display: flex; align-items: center; padding-right: 18px; border-right: 1px solid #ccd2d7; }
.institution-brand img { display: block; width: 128px; height: auto; }
.education-lockup { display: flex; align-items: baseline; gap: 10px; color: #152133; }
.education-lockup strong { font-size: 1rem; }
.education-lockup span { color: var(--muted); font-size: .78rem; }
.institution-link { margin-left: auto; color: #243445; font-size: .8rem; text-decoration: none; }
.institution-link:hover { text-decoration: underline; }
.topbar { position: sticky; top: 0; z-index: 10; display: flex; align-items: center; justify-content: space-between; gap: 24px; padding: 12px clamp(20px, 4vw, 64px); background: rgba(11, 37, 51, .97); color: white; border-bottom: 3px solid var(--amber); }
.brand { display: flex; align-items: center; gap: 12px; min-width: 230px; }
.brand-mark { display: grid; place-items: center; width: 48px; height: 48px; background: var(--amber); color: var(--deep); font-weight: 900; border-radius: 4px; letter-spacing: -.04em; transform: skew(-3deg); }
.brand div { display: flex; flex-direction: column; line-height: 1.2; }
.brand span:not(.brand-mark) { color: #b7c6cc; font-size: .78rem; }
nav { display: flex; flex-wrap: wrap; justify-content: flex-end; gap: 4px; }
.nav-button { border: 0; background: transparent; color: #c9d4d8; padding: 10px 12px; border-radius: 4px; }
.nav-button:hover, .nav-button.active { background: rgba(255,255,255,.10); color: white; }
main { width: min(1200px, calc(100% - 36px)); margin: 0 auto; padding: 48px 0 72px; }
.view { display: none; }
.view.active { display: block; animation: rise .25s ease-out; }
@keyframes rise { from { opacity: 0; transform: translateY(6px); } }
.hero { display: grid; grid-template-columns: 1fr 300px; gap: 40px; align-items: end; margin-bottom: 30px; }
.eyebrow { margin: 0 0 8px; color: var(--teal); font-size: .74rem; font-weight: 900; letter-spacing: .14em; }
h1, h2 { line-height: 1.08; margin-top: 0; letter-spacing: -.035em; }
h1 { font-family: ui-serif, Georgia, serif; font-size: clamp(2.5rem, 6vw, 5.2rem); max-width: 780px; margin-bottom: 18px; }
h2 { font-size: 1.45rem; margin-bottom: 14px; }
.hero-copy, .section-heading > p:last-child { color: var(--muted); font-size: 1.08rem; max-width: 720px; }
.hero-actions { margin-top: 24px; }
.trust-line { margin: 14px 0 0; color: var(--muted); font-size: .82rem; }
.exam-date-card { background: var(--deep); color: white; padding: 22px; border-radius: 8px; box-shadow: var(--shadow); }
.exam-date-card label, .drill-card label, .quiz-setup label { display: block; font-size: .76rem; text-transform: uppercase; font-weight: 900; letter-spacing: .08em; margin-bottom: 8px; }
.exam-date-card input, .drill-card input, select { width: 100%; border: 1px solid var(--line); border-radius: 4px; padding: 12px; background: white; color: var(--ink); }
.exam-date-card p { margin: 10px 0 0; color: #b9ccd3; font-size: .88rem; }
.metric-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin-bottom: 24px; }
.metric { padding: 18px 20px; background: #e8e3d6; border-top: 3px solid var(--teal); }
.metric span { display: block; color: var(--muted); font-size: .8rem; }
.metric strong { display: block; font-family: ui-serif, Georgia, serif; font-size: 2rem; }
.content-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
.panel { background: var(--panel); border: 1px solid var(--line); border-radius: 8px; padding: clamp(22px, 3vw, 34px); box-shadow: 0 8px 24px rgba(11,37,51,.05); }
.panel-heading { display: flex; justify-content: space-between; gap: 20px; align-items: start; }
.duration, .quiz-progress span:last-child, .drill-meta span { display: inline-flex; background: #dff0eb; color: #0a625f; border-radius: 99px; padding: 5px 10px; font-size: .72rem; font-weight: 900; text-transform: uppercase; letter-spacing: .06em; }
.task-list { padding-left: 1.2rem; margin: 18px 0 24px; }
.task-list li { margin: 10px 0; padding-left: 6px; }
.primary-action, .secondary-action { border: 0; border-radius: 4px; padding: 12px 18px; font-weight: 900; }
.primary-action { background: var(--teal); color: white; }
.primary-action:hover { background: #096963; }
.primary-action:disabled { opacity: .45; cursor: not-allowed; }
.secondary-action { background: #e4e1d8; color: var(--ink); }
.weight-row { display: grid; grid-template-columns: 170px 1fr 42px; gap: 12px; align-items: center; margin: 14px 0; font-size: .84rem; }
.weight-row div { height: 8px; background: #e0ddd4; border-radius: 99px; overflow: hidden; }
.weight-row i { display: block; height: 100%; background: var(--teal); }
.weight-row b { text-align: right; }
.number-strip { margin-top: 20px; display: grid; grid-template-columns: repeat(6, 1fr); gap: 10px; background: var(--deep); color: white; }
.number-strip div { border-right: 1px solid rgba(255,255,255,.16); }
.number-strip div:last-child { border: 0; }
.number-strip span { display: block; color: #a9c0c8; font-size: .72rem; }
.number-strip strong { font-size: 1.02rem; }
.stack-preview { margin-top: 20px; display: flex; align-items: center; justify-content: space-between; gap: 28px; border-left: 5px solid var(--amber); }
.stack-preview p { margin-bottom: 0; color: var(--muted); }
.stack-preview .primary-action { flex: 0 0 auto; }
.course-callout { margin-top: 20px; display: flex; align-items: center; justify-content: space-between; gap: 28px; background: var(--deep); color: white; border-color: var(--deep); }
.course-callout p { color: #b9ccd3; margin-bottom: 0; }
.course-callout .eyebrow { color: var(--teal-light); }
.course-callout .primary-action { flex: 0 0 auto; background: var(--amber); color: var(--deep); }
.education-foundation { margin-top: 20px; display: grid; grid-template-columns: 1.1fr 1fr; gap: 18px 34px; padding: clamp(28px, 4vw, 44px); background: #e5eef0; border: 1px solid #b8c8cd; border-radius: 8px; }
.education-foundation h2 { max-width: 500px; margin-bottom: 0; font-family: ui-serif, Georgia, serif; font-size: clamp(1.7rem, 3vw, 2.6rem); }
.education-foundation > p { margin: 4px 0 0; color: var(--muted); }
.education-principles { grid-column: 1 / -1; display: flex; flex-wrap: wrap; gap: 8px; padding-top: 4px; }
.education-principles span { padding: 7px 11px; background: white; border: 1px solid #bfd0d4; border-radius: 99px; color: #38515c; font-size: .75rem; font-weight: 900; }
.course-hero { max-width: 900px; margin-bottom: 32px; }
.course-hero h1 { font-size: clamp(2.5rem, 5.5vw, 5rem); }
.course-actions { margin-top: 24px; }
.course-actions a, .course-boundary a { text-decoration: none; display: inline-block; }
.course-freshness { margin: 14px 0 0; color: var(--muted); font-size: .82rem; }
.video-panel { margin-bottom: 20px; overflow: hidden; background: var(--deep); border-radius: 8px; box-shadow: var(--shadow); }
.video-heading { display: flex; align-items: end; justify-content: space-between; gap: 20px; padding: 24px 28px; color: white; }
.video-heading h2 { margin-bottom: 0; }
.video-heading .eyebrow { color: var(--teal-light); }
.video-heading a { flex: 0 0 auto; color: #ffd28a; }
.video-frame { position: relative; aspect-ratio: 16 / 9; background: #071a24; }
.video-frame iframe { position: absolute; inset: 0; width: 100%; height: 100%; border: 0; }
.chapter-track { margin-bottom: 20px; }
.chapter-row { display: grid; grid-template-columns: 95px 1fr 80px; gap: 18px; align-items: center; padding: 15px 0; border-top: 1px solid var(--line); }
.chapter-row time { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; color: var(--teal); font-weight: 900; }
.chapter-row div { display: flex; gap: 12px; align-items: baseline; }
.chapter-row div span { color: var(--muted); font-size: .88rem; }
.chapter-row b { text-align: right; color: var(--muted); }
.course-resource-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
.course-resource-grid p { color: var(--muted); }
.course-boundary { margin-top: 20px; border-left: 5px solid var(--amber); }
.course-boundary > p:not(.eyebrow) { max-width: 850px; color: var(--muted); }
.section-heading { margin-bottom: 32px; }
.section-heading h1 { font-size: clamp(2.2rem, 5vw, 4.4rem); margin-bottom: 10px; }
.drill-layout { grid-template-columns: 1.5fr .8fr; }
.drill-meta { display: flex; justify-content: space-between; margin-bottom: 30px; }
.drill-card h2 { font-family: ui-serif, Georgia, serif; font-size: clamp(1.6rem, 3vw, 2.4rem); min-height: 100px; }
.drill-card input { font-size: 2rem; font-weight: 800; margin-bottom: 16px; }
.button-row { display: flex; gap: 10px; }
.feedback { display: none; margin-top: 18px; padding: 16px; border-left: 4px solid var(--teal); background: #e8f2ee; }
.feedback.show { display: block; }
.feedback.wrong { border-color: var(--red); background: #f7e8e5; }
.formula-panel dl { margin: 0; }
.formula-panel dt { font-weight: 900; margin-top: 14px; }
.formula-panel dd { margin: 2px 0 0; color: var(--muted); font-family: ui-monospace, SFMono-Regular, Menlo, monospace; }
.caution { background: #fff1d7; border-left: 4px solid var(--amber); padding: 12px; margin: 24px 0 0; font-size: .88rem; }
.flashcard { width: min(800px, 100%); height: 430px; margin: 0 auto; perspective: 1200px; outline: none; }
.flashcard-inner { position: relative; width: 100%; height: 100%; transform-style: preserve-3d; transition: transform .5s; }
.flashcard.flipped .flashcard-inner { transform: rotateY(180deg); }
.flash-face { position: absolute; inset: 0; display: flex; flex-direction: column; justify-content: center; padding: clamp(30px, 6vw, 72px); border-radius: 12px; backface-visibility: hidden; box-shadow: var(--shadow); }
.flash-front { background: var(--deep); color: white; border: 1px solid #244654; }
.flash-back { background: var(--panel); border: 2px solid var(--teal); transform: rotateY(180deg); }
.flash-face span { color: var(--amber); font-size: .75rem; font-weight: 900; letter-spacing: .13em; }
.flash-face h2 { font-family: ui-serif, Georgia, serif; font-size: clamp(1.8rem, 4vw, 3.1rem); margin: 24px 0; }
.flash-face p { color: #aabdc4; }
.flash-back p { color: var(--muted); }
.card-controls { display: flex; justify-content: center; align-items: center; gap: 22px; margin-top: 24px; }
.quiz-setup { display: grid; grid-template-columns: 1fr 1fr auto; gap: 16px; align-items: end; }
.hidden { display: none !important; }
.quiz-runner { max-width: 850px; margin: 0 auto; }
.quiz-progress { display: flex; justify-content: space-between; align-items: center; color: var(--muted); font-size: .85rem; }
.progress-track { height: 5px; background: #e0ddd4; margin: 14px 0 30px; }
.progress-track i { display: block; height: 100%; background: var(--amber); width: 0; transition: width .2s; }
.quiz-runner h2 { font-family: ui-serif, Georgia, serif; font-size: clamp(1.5rem, 3vw, 2.3rem); }
.option-list { display: grid; gap: 10px; margin: 26px 0; }
.option { display: grid; grid-template-columns: 34px 1fr; gap: 10px; align-items: center; width: 100%; text-align: left; border: 1px solid var(--line); background: white; padding: 14px; border-radius: 5px; }
.option:hover, .option.selected { border-color: var(--teal); background: #edf6f3; }
.option b { display: grid; place-items: center; width: 28px; height: 28px; background: #e8e4d9; border-radius: 50%; }
.quiz-results { max-width: 900px; margin: 0 auto; }
.score-big { font-family: ui-serif, Georgia, serif; font-size: 4.5rem; line-height: 1; }
.review-item { border-top: 1px solid var(--line); padding: 20px 0; }
.review-item h3 { margin-bottom: 8px; }
.review-item p { margin: 6px 0; color: var(--muted); }
.review-item .correct { color: var(--teal); font-weight: 800; }
.review-item .incorrect { color: var(--red); font-weight: 800; }
.stack-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.stack-card { position: relative; padding-top: 54px; }
.stack-card.required { border-top: 4px solid var(--teal); }
.stack-card.optional { border-top: 4px solid var(--amber); }
.tier { position: absolute; top: 20px; left: 24px; color: var(--teal); font-size: .72rem; font-weight: 900; letter-spacing: .12em; }
.optional .tier { color: #9a5a00; }
.stack-card p { min-height: 90px; color: var(--muted); }
.resource-links { display: flex; flex-wrap: wrap; gap: 14px; }
.stack-lower { margin-top: 20px; }
.check-row { display: grid; grid-template-columns: 22px 1fr; gap: 10px; align-items: start; padding: 11px 0; border-bottom: 1px solid var(--line); cursor: pointer; }
.check-row input { width: 18px; height: 18px; accent-color: var(--teal); }
.check-row:last-of-type { margin-bottom: 18px; }
.stop-list li { margin: 10px 0; }
footer { display: grid; grid-template-columns: 1fr auto; gap: 14px 24px; align-items: start; padding: 30px clamp(20px, 4vw, 64px); background: var(--deep); color: #a9bdc5; font-size: .8rem; }
footer > div:first-child { display: flex; flex-direction: column; }
footer strong { color: white; font-size: .92rem; }
.footer-links { display: flex; gap: 16px; }
.footer-links a, .footer-links button { border: 0; padding: 0; background: transparent; color: var(--teal-light); font-weight: 800; text-decoration: none; }
footer p { grid-column: 1 / -1; max-width: 920px; margin: 0; color: #91a9b3; }

@media (max-width: 850px) {
  .topbar { position: static; display: block; padding-right: 0; }
  nav { justify-content: flex-start; flex-wrap: nowrap; margin-top: 14px; padding-right: 20px; overflow-x: auto; scrollbar-width: thin; }
  .hero, .content-grid, .drill-layout, .stack-grid, .course-hero, .course-resource-grid { grid-template-columns: 1fr; }
  .education-foundation { grid-template-columns: 1fr; }
  .education-principles { grid-column: 1; }
  .stack-preview, .course-callout { align-items: flex-start; flex-direction: column; }
  .metric-grid { grid-template-columns: repeat(2, 1fr); }
  .number-strip { grid-template-columns: repeat(3, 1fr); }
  .quiz-setup { grid-template-columns: 1fr; }
}
@media (max-width: 520px) {
  .institution-bar { min-height: 52px; gap: 12px; padding: 9px 14px; }
  .institution-brand { padding-right: 12px; }
  .institution-brand img { width: 104px; }
  .education-lockup span, .institution-link { display: none; }
  main { width: min(100% - 24px, 1200px); padding-top: 30px; }
  h1 { font-size: clamp(2.35rem, 13vw, 3.6rem); }
  .button-row { align-items: stretch; flex-direction: column; }
  .button-row > * { width: 100%; text-align: center; }
  .metric-grid { grid-template-columns: 1fr 1fr; }
  .number-strip { grid-template-columns: 1fr 1fr; }
  .weight-row { grid-template-columns: 125px 1fr 38px; }
  .flashcard { height: 480px; }
  .chapter-row { grid-template-columns: 78px 1fr; }
  .chapter-row div { display: block; }
  .chapter-row div span { display: block; margin-top: 3px; }
  .chapter-row b { display: none; }
  .video-heading { align-items: flex-start; flex-direction: column; padding: 20px; }
  footer { grid-template-columns: 1fr; }
  .footer-links, footer p { grid-column: 1; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
}