:root {
  color-scheme: light dark;
  --bg: #f4f7fb;
  --bg-soft: #eaf0f8;
  --surface: rgba(255,255,255,.7);
  --surface-solid: #fff;
  --text: #101522;
  --muted: #657086;
  --line: rgba(20,31,51,.12);
  --line-strong: rgba(20,31,51,.22);
  --blue: #3478f6;
  --violet: #7457f5;
  --coral: #ef6d86;
  --green: #158864;
  --shadow: 0 18px 55px rgba(35,52,84,.11);
  --shadow-soft: 0 8px 28px rgba(35,52,84,.09);
  --radius-xl: 30px;
  --radius-l: 22px;
  --radius-m: 15px;
  --spring: cubic-bezier(.2,.9,.2,1);
  --shell: 1180px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0c111a;
    --bg-soft: #121927;
    --surface: rgba(27,34,48,.72);
    --surface-solid: #1b2331;
    --text: #f5f7fb;
    --muted: #a7b0c1;
    --line: rgba(229,235,247,.12);
    --line-strong: rgba(229,235,247,.24);
    --blue: #76a1ff;
    --violet: #a08bff;
    --coral: #ff8da0;
    --green: #5bc59e;
    --shadow: 0 20px 60px rgba(0,0,0,.34);
    --shadow-soft: 0 10px 32px rgba(0,0,0,.24);
  }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; font: 100%/1.5 ui-sans-serif,-apple-system,BlinkMacSystemFont,"SF Pro Text","Helvetica Neue",Arial,sans-serif; }
body {
  margin: 0;
  color: var(--text);
  background:
    radial-gradient(900px 560px at 8% 0%, color-mix(in srgb,var(--blue) 13%,transparent), transparent 65%),
    radial-gradient(820px 500px at 96% 12%, color-mix(in srgb,var(--violet) 11%,transparent), transparent 66%),
    var(--bg);
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; }
button, a { -webkit-tap-highlight-color: transparent; }
button { font: inherit; }
h1, h2, h3, p { margin-top: 0; }
h1 { margin-bottom: 24px; font-size: clamp(3.1rem,7vw,6.2rem); font-weight: 760; letter-spacing: -.06em; line-height: .96; text-wrap: balance; }
h1 span { color: transparent; background: linear-gradient(120deg,var(--blue),var(--violet) 55%,var(--coral)); -webkit-background-clip: text; background-clip: text; }
h2 { margin-bottom: 16px; font-size: clamp(2rem,4vw,3.25rem); font-weight: 730; letter-spacing: -.045em; line-height: 1.07; text-wrap: balance; }
h3 { font-size: 1.1rem; letter-spacing: -.02em; }
.shell { width: min(var(--shell),calc(100% - 40px)); margin-inline: auto; }
.glass { border: 1px solid var(--line); background: var(--surface); box-shadow: var(--shadow-soft); backdrop-filter: blur(22px) saturate(160%); -webkit-backdrop-filter: blur(22px) saturate(160%); }

.nav { position: sticky; z-index: 20; top: 0; border-bottom: 1px solid var(--line); background: color-mix(in srgb,var(--bg) 72%,transparent); backdrop-filter: blur(22px) saturate(170%); -webkit-backdrop-filter: blur(22px) saturate(170%); }
.nav-inner { width: min(var(--shell),calc(100% - 40px)); min-height: 68px; margin: auto; display: flex; align-items: center; gap: 28px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 700; letter-spacing: -.02em; text-decoration: none; white-space: nowrap; }
.brand-symbol { width: 30px; height: 30px; overflow: visible; fill: var(--surface-solid); stroke: var(--blue); stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
.nav-links { display: flex; gap: 22px; margin-left: auto; }
.nav-links a { color: var(--muted); font-size: .9rem; text-decoration: none; }
.nav-links a:hover { color: var(--text); }
.progress-compact { min-width: 126px; display: flex; align-items: center; gap: 9px; color: var(--muted); font-size: .78rem; }
.progress-track { width: 70px; height: 5px; overflow: hidden; border-radius: 999px; background: var(--line); }
.progress-track i { display: block; width: 0; height: 100%; border-radius: inherit; background: linear-gradient(90deg,var(--blue),var(--violet)); transition: width .4s var(--spring); }

.hero { position: relative; overflow: clip; padding: clamp(72px,10vw,132px) 0 88px; }
.hero-grid { display: grid; grid-template-columns: .88fr 1.12fr; align-items: center; gap: clamp(44px,7vw,88px); }
.eyebrow, .section-index { margin: 0 0 14px; color: var(--blue); font-size: .74rem; font-weight: 700; letter-spacing: .13em; text-transform: uppercase; }
.lede { max-width: 60ch; margin-bottom: 30px; color: var(--muted); font-size: clamp(1.03rem,1.5vw,1.2rem); line-height: 1.72; }
.actions { display: flex; flex-wrap: wrap; gap: 12px; }
.button { min-height: 48px; display: inline-flex; align-items: center; justify-content: center; padding: 0 19px; border: 1px solid var(--line); border-radius: 14px; color: var(--text); background: var(--surface-solid); box-shadow: 0 1px 0 color-mix(in srgb,white 70%,transparent) inset; font-weight: 650; text-decoration: none; cursor: pointer; transition: transform .28s var(--spring),box-shadow .28s var(--spring),background .2s ease; }
.button:hover { transform: translateY(-2px) scale(1.015); box-shadow: var(--shadow-soft); }
.button:active { transform: scale(.97); transition-duration: .08s; }
.button-primary { border-color: transparent; color: white; background: linear-gradient(120deg,var(--blue),var(--violet)); box-shadow: 0 9px 24px color-mix(in srgb,var(--blue) 25%,transparent); }
.button-primary.is-done { background: var(--green); }
.hero-metrics { display: flex; gap: 28px; margin: 36px 0 0; }
.hero-metrics div { display: grid; }
.hero-metrics dt { font-size: 1.7rem; font-weight: 750; letter-spacing: -.045em; }
.hero-metrics dd { margin: 0; color: var(--muted); font-size: .8rem; }
.hero-visual { position: relative; margin: 0; overflow: hidden; border-radius: var(--radius-xl); }
.hero-visual figcaption { position: absolute; z-index: 2; top: 22px; left: 24px; color: var(--muted); font-size: .78rem; font-weight: 650; }
.hero-visual svg { width: 100%; height: auto; display: block; }
.soft-orbit circle { fill: none; stroke: var(--line); stroke-width: 1; stroke-dasharray: 4 8; }
.argument-path { fill: none; stroke: url(#hero-flow); stroke-width: 2.5; stroke-linecap: round; stroke-dasharray: 8 8; animation: dash-flow 12s linear infinite; }
.path-b, .path-c { animation-direction: reverse; }
.core-glow { fill: color-mix(in srgb,var(--blue) 34%,transparent); opacity: .7; }
.svg-node circle { fill: var(--surface-solid); stroke: var(--line-strong); stroke-width: 1.4; transform-box: fill-box; transform-origin: center; }
.svg-node text { fill: var(--text); font-size: 13px; font-weight: 700; letter-spacing: .06em; text-anchor: middle; }
.svg-node .svg-sub { fill: var(--muted); font-size: 10px; font-weight: 500; letter-spacing: 0; }
.node-core circle { fill: url(#hero-flow); stroke: transparent; }
.node-core text { fill: white; }
.node-core .svg-sub { fill: rgba(255,255,255,.75); }
.node-proof circle { animation: float-a 7s ease-in-out infinite alternate; }
.node-objection circle { animation: float-b 8s ease-in-out infinite alternate; }
.node-nuance circle { animation: float-b 9s ease-in-out infinite alternate-reverse; }
.node-conclusion circle { animation: float-a 8.5s ease-in-out infinite alternate-reverse; }
.visual-caption { display: flex; align-items: center; gap: 10px; padding: 16px 22px 20px; border-top: 1px solid var(--line); color: var(--muted); font-size: .84rem; }
.pulse-dot { width: 8px; height: 8px; flex: none; border-radius: 50%; background: var(--green); box-shadow: 0 0 0 7px color-mix(in srgb,var(--green) 14%,transparent); }
@keyframes dash-flow { to { stroke-dashoffset: -96; } }
@keyframes float-a { to { transform: translateY(-5px); } }
@keyframes float-b { to { transform: translate(5px,3px); } }

.section { padding: 100px 0; }
.section-tinted { border-block: 1px solid var(--line); background: color-mix(in srgb,var(--bg-soft) 72%,transparent); }
.section-heading { display: grid; grid-template-columns: 1.4fr .6fr; align-items: end; gap: 42px; margin-bottom: 42px; }
.section-heading h2 { margin-bottom: 0; }
.section-heading > p { margin: 0 0 6px; color: var(--muted); line-height: 1.7; }
.roadmap-wrap { overflow: hidden; border-radius: var(--radius-xl); }
.roadmap { width: 100%; min-width: 760px; display: block; }
.road-line, .road-progress { fill: none; stroke-linecap: round; stroke-linejoin: round; stroke-width: 10; }
.road-line { stroke: var(--line); }
.road-progress { stroke: url(#road-gradient); stroke-dasharray: 0 100; transition: stroke-dasharray .7s var(--spring); }
.road-node { color: var(--muted); cursor: pointer; }
.road-node circle { fill: var(--surface-solid); stroke: var(--line-strong); stroke-width: 2; transition: transform .28s var(--spring),fill .2s ease,stroke .2s ease; transform-box: fill-box; transform-origin: center; }
.road-node text { fill: currentColor; font-size: 13px; font-weight: 700; text-anchor: middle; pointer-events: none; }
.road-node:hover circle, .road-node:focus circle { transform: scale(1.13); }
.road-node.done circle { fill: var(--green); stroke: transparent; }
.road-node.done text { fill: white; }
.road-node.next { color: var(--text); }
.road-node.next circle { stroke: var(--blue); stroke-width: 4; filter: drop-shadow(0 5px 8px color-mix(in srgb,var(--blue) 28%,transparent)); }
.road-label { fill: var(--muted); font-size: 12px; font-weight: 650; letter-spacing: .08em; }
.roadmap-legend { display: flex; flex-wrap: wrap; gap: 18px; padding: 0 24px 22px; color: var(--muted); font-size: .75rem; }
.roadmap-legend span { display: inline-flex; align-items: center; gap: 7px; }
.legend-dot { width: 9px; height: 9px; border: 1px solid var(--line-strong); border-radius: 50%; }
.legend-dot.done { border-color: var(--green); background: var(--green); }
.legend-dot.next { border: 2px solid var(--blue); }
.module-grid { display: grid; grid-template-columns: repeat(4,1fr); gap: 14px; margin-top: 18px; }
.module-card { min-height: 210px; padding: 24px; border: 1px solid var(--line); border-radius: var(--radius-l); background: var(--surface); transition: transform .3s var(--spring),background .2s ease,box-shadow .3s var(--spring); }
.module-card:hover { transform: translateY(-4px); background: var(--surface-solid); box-shadow: var(--shadow-soft); }
.module-number { display: flex; justify-content: space-between; margin-bottom: 36px; color: var(--blue); font-size: .75rem; font-weight: 700; letter-spacing: .08em; }
.module-card h3 { margin-bottom: 10px; }
.module-card p { margin: 0; color: var(--muted); font-size: .88rem; line-height: 1.65; }
.lesson-list { border-top: 1px solid var(--line); }
.lesson-row { display: grid; grid-template-columns: 54px 1.25fr 1fr auto; align-items: center; gap: 22px; min-height: 98px; border-bottom: 1px solid var(--line); text-decoration: none; transition: padding .3s var(--spring),background .2s ease; }
.lesson-row:hover { padding-inline: 14px; background: color-mix(in srgb,var(--surface-solid) 68%,transparent); }
.lesson-number { color: var(--muted); font-size: .8rem; font-variant-numeric: tabular-nums; }
.lesson-row h3 { margin: 0 0 4px; }
.lesson-row p { margin: 0; color: var(--muted); font-size: .84rem; }
.lesson-skill { color: var(--muted); font-size: .84rem; }
.lesson-state { min-width: 88px; padding: 7px 10px; border: 1px solid var(--line); border-radius: 999px; color: var(--muted); font-size: .72rem; text-align: center; }
.lesson-state.done { border-color: color-mix(in srgb,var(--green) 45%,transparent); color: var(--green); background: color-mix(in srgb,var(--green) 9%,transparent); }
footer { padding: 34px 0 48px; color: var(--muted); font-size: .82rem; }
.footer-inner { display: flex; justify-content: space-between; gap: 20px; }

.lesson-nav { display: flex; align-items: center; gap: 12px; margin-left: auto; color: var(--muted); font-size: .78rem; }
.icon-button { width: 36px; height: 36px; display: grid; place-items: center; border: 1px solid var(--line); border-radius: 50%; background: var(--surface); text-decoration: none; transition: transform .2s var(--spring),background .2s ease; }
.icon-button:hover { transform: scale(1.07); background: var(--surface-solid); }
.icon-button:active { transform: scale(.94); }
.lesson-hero { padding: 82px 0 64px; border-bottom: 1px solid var(--line); }
.lesson-hero-grid { display: grid; grid-template-columns: 1fr 280px; align-items: end; gap: 70px; }
.lesson-hero h1 { max-width: 800px; font-size: clamp(3rem,6vw,5.5rem); }
.skill-row { display: flex; flex-wrap: wrap; gap: 8px; }
.skill-chip { padding: 7px 11px; border: 1px solid var(--line); border-radius: 999px; color: var(--muted); background: var(--surface); font-size: .76rem; }
.lesson-status { display: grid; gap: 10px; padding: 22px; border-radius: var(--radius-l); }
.lesson-status > span { color: var(--muted); font-size: .75rem; }
.lesson-status > strong { margin-bottom: 8px; font-size: 1.25rem; letter-spacing: -.03em; }
.lesson-layout { display: grid; grid-template-columns: minmax(0,820px) 250px; align-items: start; gap: 70px; padding-block: 72px 120px; }
.lesson-layout > article { min-width: 0; }
.content-section { padding: 42px 0 68px; border-bottom: 1px solid var(--line); scroll-margin-top: 90px; }
.content-section:first-child { padding-top: 0; }
.content-section h2 { font-size: clamp(1.9rem,3.2vw,2.7rem); }
.objectives { padding: 28px; border: 1px solid color-mix(in srgb,var(--blue) 24%,var(--line)); border-radius: var(--radius-l); background: color-mix(in srgb,var(--blue) 7%,var(--surface)); }
.objective-list { display: grid; gap: 12px; margin: 24px 0 0; padding: 0; list-style: none; }
.objective-list li { position: relative; padding-left: 26px; color: var(--muted); }
.objective-list li::before { content: ""; position: absolute; top: .48em; left: 2px; width: 9px; height: 9px; border: 2px solid var(--blue); border-radius: 50%; }
.content-heading { display: flex; align-items: end; justify-content: space-between; gap: 30px; }
.concept-detail { max-width: 290px; margin-bottom: 19px; color: var(--muted); font-size: .82rem; text-align: right; }
.concept-figure { margin: 16px 0 0; overflow: hidden; border-radius: var(--radius-l); }
.concept-figure svg { width: 100%; height: auto; display: block; }
.concept-line { fill: none; stroke: url(#concept-gradient); stroke-width: 3; stroke-linecap: round; opacity: .42; }
.concept-node { cursor: pointer; outline: none; }
.concept-node circle { fill: var(--surface-solid); stroke: var(--line-strong); stroke-width: 2; transition: transform .28s var(--spring),stroke .2s ease,fill .2s ease; transform-box: fill-box; transform-origin: center; }
.concept-node:hover circle, .concept-node:focus circle { transform: scale(1.055); stroke: var(--blue); }
.concept-node.active circle { fill: url(#concept-gradient); stroke: transparent; }
.concept-node text { fill: var(--text); font-size: 15px; font-weight: 680; text-anchor: middle; pointer-events: none; }
.concept-node .concept-sub { fill: var(--muted); font-size: 11px; font-weight: 500; }
.concept-node.active text { fill: white; }
.concept-node.active .concept-sub { fill: rgba(255,255,255,.76); }
.formula { display: grid; gap: 8px; margin: 26px 0; padding: 24px; border-radius: var(--radius-l); }
.formula span { color: var(--blue); font-size: .71rem; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; }
.formula strong { font-size: clamp(1.1rem,2vw,1.45rem); line-height: 1.5; }
.explanation-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 14px; }
.explanation-card { padding: 20px; border: 1px solid var(--line); border-radius: var(--radius-m); }
.explanation-card span { display: block; margin-bottom: 12px; color: var(--blue); font-size: .7rem; font-weight: 700; letter-spacing: .08em; }
.explanation-card h3 { margin-bottom: 8px; }
.explanation-card p { margin: 0; color: var(--muted); font-size: .85rem; line-height: 1.65; }
.example-block { margin: 20px 0 0; padding: 28px 30px; border-left: 3px solid var(--violet); background: color-mix(in srgb,var(--violet) 7%,transparent); }
.example-block p { margin-bottom: 8px; font-size: 1.2rem; font-weight: 620; line-height: 1.55; }
.example-block footer { padding: 0; color: var(--muted); font-size: .9rem; }
.vocab-grid { display: grid; grid-template-columns: repeat(2,1fr); gap: 1px; overflow: hidden; border: 1px solid var(--line); border-radius: var(--radius-l); background: var(--line); }
.vocab-item { display: grid; grid-template-columns: .85fr 1.15fr; gap: 14px; padding: 18px 20px; background: var(--surface-solid); }
.vocab-item strong { font-size: .92rem; }
.vocab-item span { color: var(--muted); font-size: .82rem; }
.dialogue { overflow: hidden; border-radius: var(--radius-l); }
.dialogue-line { display: grid; grid-template-columns: 42px 1fr; gap: 16px; padding: 24px; border-bottom: 1px solid var(--line); }
.dialogue-line:last-child { border-bottom: 0; }
.speaker { width: 38px; height: 38px; display: grid; place-items: center; border-radius: 50%; color: white; background: linear-gradient(135deg,var(--blue),var(--violet)); font-weight: 700; }
.dialogue-copy strong { display: block; margin-bottom: 6px; }
.dialogue-copy p { margin-bottom: 5px; line-height: 1.6; }
.dialogue-copy .translation { margin-bottom: 0; color: var(--muted); font-size: .84rem; }
.quiz-list { display: grid; gap: 16px; }
.quiz-card { padding: 24px; border: 1px solid var(--line); border-radius: var(--radius-l); background: var(--surface); }
.quiz-number { color: var(--blue); font-size: .7rem; font-weight: 700; letter-spacing: .1em; }
.quiz-question { margin: 12px 0 16px; font-size: 1.05rem; font-weight: 650; }
.quiz-options { display: grid; gap: 9px; }
.quiz-option { width: 100%; padding: 13px 15px; border: 1px solid var(--line); border-radius: 12px; color: var(--text); background: var(--surface-solid); text-align: left; cursor: pointer; transition: transform .12s ease,border-color .2s ease,background .2s ease; }
.quiz-option:hover:not(:disabled) { border-color: var(--blue); transform: translateX(3px); }
.quiz-option:active:not(:disabled) { transform: scale(.99); }
.quiz-option.correct { border-color: var(--green); background: color-mix(in srgb,var(--green) 12%,var(--surface-solid)); }
.quiz-option.wrong { border-color: var(--coral); background: color-mix(in srgb,var(--coral) 10%,var(--surface-solid)); }
.quiz-option:disabled { color: var(--muted); cursor: default; }
.quiz-feedback { min-height: 1.5em; margin: 12px 0 0; color: var(--muted); font-size: .86rem; }
.production { margin-top: 44px; padding: 34px; border: 1px solid color-mix(in srgb,var(--violet) 26%,var(--line)); border-radius: var(--radius-xl); }
.production-line { height: 1px; margin: 28px 0; background: linear-gradient(90deg,var(--violet),transparent); }
.takeaway { margin-bottom: 0; color: var(--muted); font-style: italic; }
.lesson-pager { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin-top: 38px; }
.lesson-pager a { min-height: 94px; display: grid; align-content: center; gap: 6px; padding: 18px 20px; border: 1px solid var(--line); border-radius: var(--radius-l); background: var(--surface); text-decoration: none; }
.lesson-pager a:last-child { text-align: right; }
.lesson-pager span { color: var(--muted); font-size: .78rem; }
.lesson-pager strong { line-height: 1.3; }
.lesson-aside { position: sticky; top: 96px; }
.aside-inner { display: grid; gap: 8px; padding: 22px; border-radius: var(--radius-l); }
.aside-title { margin-bottom: 8px; font-weight: 700; }
.aside-inner a { padding: 5px 0; color: var(--muted); font-size: .84rem; text-decoration: none; }
.aside-inner a:hover { color: var(--text); }
.aside-inner > span { margin-top: 12px; padding-top: 14px; border-top: 1px solid var(--line); color: var(--muted); font-size: .76rem; }

@media (max-width: 980px) {
  .hero-grid { grid-template-columns: 1fr; }
  .hero-copy, .hero-visual { max-width: 760px; }
  .module-grid { grid-template-columns: repeat(2,1fr); }
  .lesson-layout { grid-template-columns: 1fr; }
  .lesson-aside { display: none; }
}
@media (max-width: 760px) {
  .shell, .nav-inner { width: min(calc(100% - 28px),var(--shell)); }
  .nav-links { display: none; }
  .progress-compact { margin-left: auto; min-width: auto; }
  .progress-track { width: 44px; }
  .hero { padding-top: 64px; }
  .hero-metrics { justify-content: space-between; gap: 12px; }
  .section { padding: 76px 0; }
  .section-heading { grid-template-columns: 1fr; gap: 14px; }
  .roadmap-wrap, .concept-figure { overflow-x: auto; }
  .module-grid { grid-template-columns: 1fr; }
  .lesson-row { grid-template-columns: 40px 1fr auto; gap: 12px; min-height: 92px; }
  .lesson-skill { display: none; }
  .lesson-state { min-width: 70px; }
  .lesson-hero-grid { grid-template-columns: 1fr; gap: 34px; }
  .lesson-status { max-width: 520px; }
  .content-heading { display: block; }
  .concept-detail { max-width: none; text-align: left; }
  .concept-figure svg { min-width: 720px; }
  .explanation-grid { grid-template-columns: 1fr; }
  .vocab-grid { grid-template-columns: 1fr; }
}
@media (max-width: 480px) {
  .brand span { display: none; }
  h1 { font-size: clamp(2.85rem,14vw,4.15rem); }
  .hero-copy h1 { font-size: clamp(3rem,15vw,4.4rem); }
  .actions .button { width: 100%; }
  .hero-visual figcaption { position: static; padding: 18px 18px 0; }
  .hero-metrics dt { font-size: 1.45rem; }
  .lesson-hero { padding-top: 56px; }
  .lesson-layout { padding-top: 52px; }
  .objectives, .production { padding: 24px 20px; }
  .dialogue-line { grid-template-columns: 36px 1fr; padding: 20px 16px; }
  .speaker { width: 34px; height: 34px; }
  .lesson-pager { grid-template-columns: 1fr; }
  .lesson-pager a:last-child { text-align: left; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
}
@media (prefers-reduced-transparency: reduce) {
  .glass, .nav { background: var(--surface-solid); backdrop-filter: none; -webkit-backdrop-filter: none; }
}
@media (prefers-contrast: more) {
  :root { --line: color-mix(in srgb,var(--text) 42%,transparent); --line-strong: color-mix(in srgb,var(--text) 68%,transparent); }
  .glass, .module-card, .lesson-row, .quiz-card { background: var(--bg); }
}