:root {
  color-scheme: light dark;
  --bg: #f2f5f9;
  --bg-deep: #e8edf5;
  --surface: rgba(255, 255, 255, .68);
  --surface-strong: rgba(255, 255, 255, .9);
  --text: #111827;
  --muted: #657084;
  --line: rgba(21, 32, 51, .11);
  --line-strong: rgba(21, 32, 51, .2);
  --blue: #246bfd;
  --violet: #7a5cff;
  --coral: #ff6b72;
  --green: #1f9d72;
  --gold: #d39122;
  --shadow: 0 24px 70px rgba(29, 49, 83, .12);
  --shadow-soft: 0 10px 30px rgba(29, 49, 83, .08);
  --radius-xl: 32px;
  --radius-l: 24px;
  --radius-m: 16px;
  --spring: cubic-bezier(.2, .9, .2, 1);
  --shell: 1180px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0d1119;
    --bg-deep: #121927;
    --surface: rgba(27, 34, 47, .7);
    --surface-strong: rgba(31, 39, 54, .94);
    --text: #f5f7fb;
    --muted: #a5aec0;
    --line: rgba(225, 233, 246, .12);
    --line-strong: rgba(225, 233, 246, .23);
    --blue: #6f9cff;
    --violet: #a28cff;
    --coral: #ff858c;
    --green: #61c9a3;
    --gold: #efb85a;
    --shadow: 0 28px 80px rgba(0, 0, 0, .3);
    --shadow-soft: 0 12px 36px rgba(0, 0, 0, .22);
  }
}

* { 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) 14%, transparent), transparent 65%),
    radial-gradient(820px 500px at 96% 12%, color-mix(in srgb, var(--violet) 12%, transparent), transparent 66%),
    var(--bg);
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; }
button, a { -webkit-tap-highlight-color: transparent; }
button { font: inherit; }

.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(24px) saturate(165%);
  -webkit-backdrop-filter: blur(24px) saturate(165%);
}

.nav {
  position: sticky;
  z-index: 20;
  top: 0;
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 68%, 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-strong);
  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 .45s var(--spring);
}

.hero {
  position: relative;
  overflow: clip;
  padding: clamp(76px, 10vw, 138px) 0 90px;
}

.hero-grid {
  display: grid;
  grid-template-columns: .88fr 1.12fr;
  align-items: center;
  gap: clamp(48px, 7vw, 92px);
}

.eyebrow,
.section-index {
  margin: 0 0 14px;
  color: var(--blue);
  font-size: .74rem;
  font-weight: 700;
  letter-spacing: .13em;
  text-transform: uppercase;
}

h1, h2, h3, p { margin-top: 0; }

h1 {
  margin-bottom: 24px;
  font-size: clamp(3.35rem, 7vw, 6.4rem);
  font-weight: 760;
  letter-spacing: -.065em;
  line-height: .94;
  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, 3.35rem);
  font-weight: 730;
  letter-spacing: -.045em;
  line-height: 1.06;
  text-wrap: balance;
}

h3 {
  font-size: 1.12rem;
  letter-spacing: -.02em;
}

.lede {
  max-width: 60ch;
  margin-bottom: 30px;
  color: var(--muted);
  font-size: clamp(1.05rem, 1.5vw, 1.22rem);
  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-strong);
  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: translateY(0) 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 {
  color: white;
  background: var(--green);
  box-shadow: 0 9px 24px color-mix(in srgb, var(--green) 22%, transparent);
}

.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-strong);
  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, .74); }

.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: translate(0, -5px); } }
@keyframes float-b { to { transform: translate(5px, 3px); } }

.section { padding: 104px 0; }

.section-tinted {
  border-block: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg-deep) 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;
}

.road-line {
  stroke: var(--line);
  stroke-width: 10;
}

.road-progress {
  stroke: url(#road-gradient);
  stroke-width: 10;
  stroke-dasharray: 0 100;
  transition: stroke-dasharray .75s var(--spring);
}

.road-node {
  color: var(--muted);
  cursor: pointer;
}

.road-node circle {
  fill: var(--surface-strong);
  stroke: var(--line-strong);
  stroke-width: 2;
  transition: transform .28s var(--spring), fill .28s ease, stroke .28s 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-strong);
  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-strong) 66%, 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 */
.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-strong); }
.icon-button:active { transform: scale(.94); }

.lesson-hero {
  padding: 84px 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, 5.6rem);
}

.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-strong);
  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: 1.23rem; 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-strong);
}

.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: 14px;
  padding: 22px 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: var(--blue);
  font-size: .76rem;
  font-weight: 750;
}

.dialogue-line:nth-child(even) .speaker { background: var(--violet); }
.dialogue-copy strong { display: block; margin-bottom: 6px; font-size: .78rem; }
.dialogue-copy p { margin: 0; line-height: 1.62; }
.dialogue-copy .translation { margin-top: 7px; color: var(--muted); font-size: .82rem; }

.quiz-list { display: grid; gap: 14px; }

.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: 9px 0 18px; font-weight: 650; line-height: 1.55; }
.quiz-options { display: grid; gap: 8px; }

.quiz-option {
  width: 100%;
  min-height: 45px;
  padding: 10px 14px;
  border: 1px solid var(--line);
  border-radius: 12px;
  color: var(--text);
  background: var(--surface-strong);
  text-align: left;
  cursor: pointer;
  transition: transform .15s var(--spring), border-color .15s ease, background .15s ease;
}

.quiz-option:hover { border-color: var(--blue); transform: translateX(2px); }
.quiz-option:active { transform: scale(.985); }
.quiz-option:disabled { cursor: default; }
.quiz-option.correct { border-color: var(--green); background: color-mix(in srgb, var(--green) 12%, var(--surface-strong)); }
.quiz-option.wrong { border-color: var(--coral); background: color-mix(in srgb, var(--coral) 10%, var(--surface-strong)); }

.quiz-feedback {
  min-height: 1.4em;
  margin: 13px 0 0;
  color: var(--muted);
  font-size: .82rem;
}

.production {
  margin-top: 56px;
  padding: 32px;
  border-radius: var(--radius-l);
}

.production > p:not(.section-index):not(.takeaway) { font-size: 1.08rem; line-height: 1.75; }

.production-line {
  height: 110px;
  margin: 24px 0;
  background: repeating-linear-gradient(to bottom, transparent 0 31px, var(--line) 31px 32px);
}

.takeaway {
  margin: 0;
  padding-top: 20px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: .9rem;
  font-style: italic;
}

.lesson-pager {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  padding-top: 50px;
}

.lesson-pager a {
  min-height: 108px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 22px;
  border: 1px solid var(--line);
  border-radius: var(--radius-l);
  background: var(--surface);
  text-decoration: none;
  transition: transform .25s var(--spring), background .2s ease;
}

.lesson-pager a:hover { transform: translateY(-3px); background: var(--surface-strong); }
.lesson-pager a:last-child { align-items: flex-end; text-align: right; }
.lesson-pager span { margin-bottom: 5px; color: var(--muted); font-size: .73rem; }

.lesson-aside { position: sticky; top: 94px; }

.aside-inner {
  display: grid;
  gap: 4px;
  padding: 18px;
  border-radius: var(--radius-m);
}

.aside-title {
  margin: 0 0 9px;
  font-size: .78rem;
  font-weight: 700;
}

.aside-inner a {
  padding: 8px 9px;
  border-radius: 9px;
  color: var(--muted);
  font-size: .8rem;
  text-decoration: none;
}

.aside-inner a:hover { color: var(--text); background: color-mix(in srgb, var(--blue) 8%, transparent); }
.aside-inner > span { margin-top: 10px; padding-top: 13px; border-top: 1px solid var(--line); color: var(--muted); font-size: .73rem; }

@media (max-width: 980px) {
  .hero-grid { grid-template-columns: 1fr; }
  .hero-copy { max-width: 760px; }
  .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(100% - 28px, var(--shell)); }
  .nav-links { display: none; }
  .progress-compact { margin-left: auto; min-width: auto; }
  .progress-track { width: 44px; }
  .hero { padding-top: 64px; }
  h1 { font-size: clamp(3rem, 16vw, 4.8rem); }
  .section { padding: 76px 0; }
  .section-heading { grid-template-columns: 1fr; gap: 14px; }
  .roadmap-wrap { 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 { padding-top: 58px; }
  .lesson-hero-grid { grid-template-columns: 1fr; gap: 28px; }
  .lesson-status { grid-template-columns: 1fr auto; align-items: center; }
  .lesson-status > span { grid-column: 1; }
  .lesson-status > strong { grid-column: 1; margin: 0; }
  .lesson-status .button { grid-column: 2; grid-row: 1 / 3; }
  .content-heading { display: block; }
  .concept-detail { max-width: none; text-align: left; }
  .concept-figure { overflow-x: auto; }
  .concept-figure svg { min-width: 720px; }
  .explanation-grid { grid-template-columns: 1fr; }
  .vocab-grid { grid-template-columns: 1fr; }
  .lesson-pager { grid-template-columns: 1fr; }
}

@media (max-width: 480px) {
  .brand span { display: none; }
  .hero-metrics { justify-content: space-between; gap: 14px; }
  .hero-visual > figcaption { position: static; padding: 18px 18px 0; }
  .actions .button { flex: 1 1 100%; }
  .lesson-status { display: grid; grid-template-columns: 1fr; }
  .lesson-status .button { grid-column: 1; grid-row: auto; }
  .vocab-item { grid-template-columns: 1fr; gap: 4px; }
  .dialogue-line { padding: 18px; }
  .production { padding: 24px; }
  .footer-inner { flex-direction: column; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    scroll-behavior: auto !important;
    animation: none !important;
    transition-duration: .01ms !important;
  }
}

@media (prefers-reduced-transparency: reduce) {
  .glass,
  .nav {
    background: var(--surface-strong);
    backdrop-filter: none;
    -webkit-backdrop-filter: none;
  }
}

@media (prefers-contrast: more) {
  :root { --line: currentColor; --line-strong: currentColor; }
  .glass, .module-card, .lesson-row, .quiz-card { background: var(--bg); }
}