:root {
  --bg: #0c1114;
  --surface: #151c20;
  --surface-2: #1c252a;
  --surface-3: #10171b;
  --line: #34434b;
  --line-strong: #50616a;
  --text: #f4f7f8;
  --muted: #aab7be;
  --green: #61e3a5;
  --blue: #6bbcff;
  --yellow: #ffd166;
  --red: #ff7b7b;
  --purple: #b8a1ff;
  --ink: #0c1114;
  --content: 1240px;
  --font-display: "Space Grotesk", Inter, system-ui, sans-serif;
  --font-mono: "DM Mono", Consolas, monospace;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  isolation: isolate;
  margin: 0;
  overflow-x: hidden;
  background:
    linear-gradient(rgba(107, 188, 255, .025) 1px, transparent 1px),
    linear-gradient(90deg, rgba(107, 188, 255, .025) 1px, transparent 1px),
    var(--bg);
  background-size: 48px 48px;
  color: var(--text);
  font-family: var(--font-display);
  line-height: 1.6;
}

body::before {
  position: fixed;
  z-index: 0;
  inset: -20% auto auto 58%;
  width: 620px;
  height: 620px;
  border-radius: 50%;
  background: rgba(97, 227, 165, .055);
  filter: blur(120px);
  content: "";
  pointer-events: none;
}

#matrix-background {
  position: fixed;
  z-index: 0;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: .72;
  pointer-events: none;
}

main,
.site-footer {
  position: relative;
  z-index: 1;
}

a { color: inherit; }

a:focus-visible,
button:focus-visible,
iframe:focus-visible {
  outline: 3px solid rgba(107, 188, 255, .5);
  outline-offset: 4px;
}

.skip-link {
  position: fixed;
  z-index: 100;
  top: 12px;
  left: 12px;
  padding: 9px 13px;
  border-radius: 7px;
  color: var(--ink);
  background: var(--green);
  font-weight: 800;
  text-decoration: none;
  transform: translateY(-160%);
}

.skip-link:focus { transform: translateY(0); }

.site-header {
  position: sticky;
  z-index: 20;
  top: 0;
  padding: 18px 24px 0;
  pointer-events: none;
}

.topbar,
main,
.footer-inner {
  width: min(var(--content), calc(100% - 48px));
  margin: 0 auto;
}

.topbar {
  display: flex;
  min-height: 68px;
  align-items: center;
  justify-content: space-between;
  gap: 28px;
  padding: 10px 12px 10px 18px;
  border: 1px solid rgba(244, 247, 248, .12);
  border-radius: 16px;
  background: rgba(12, 17, 20, .86);
  box-shadow: 0 16px 44px rgba(0, 0, 0, .22);
  backdrop-filter: blur(16px);
  pointer-events: auto;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  color: var(--text);
  text-decoration: none;
}

.brand-mark {
  display: grid;
  width: 38px;
  height: 38px;
  place-items: center;
  border: 1px solid #4a725f;
  border-radius: 9px;
  color: var(--green);
  background: #143426;
  font: 500 .72rem/1 var(--font-mono);
}

.brand-copy,
.brand-copy strong,
.brand-copy small { display: block; }

.brand-copy strong {
  font-size: .96rem;
  letter-spacing: -.04em;
}

.brand-copy strong span { color: var(--green); }

.brand-copy small {
  color: var(--muted);
  font: 400 .63rem/1.45 var(--font-mono);
  letter-spacing: .02em;
}

.topnav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: flex-end;
  gap: 6px 22px;
}

.topnav a {
  color: var(--muted);
  font-size: .79rem;
  font-weight: 650;
  text-decoration: none;
  transition: color .2s ease;
}

.topnav a:hover,
.topnav a:focus-visible { color: var(--green); }

.topnav .nav-profile {
  padding: 9px 12px;
  border: 1px solid var(--line);
  border-radius: 9px;
  color: var(--text);
  background: rgba(244, 247, 248, .04);
}

.topnav .nav-profile:hover { border-color: var(--green); }

main { padding-bottom: 72px; }

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

h1,
h2,
h3 {
  color: var(--text);
  letter-spacing: -.055em;
}

h1 {
  max-width: 830px;
  margin-bottom: 23px;
  font-size: clamp(3rem, 5.1vw, 5.5rem);
  font-weight: 700;
  line-height: .86;
  text-transform: uppercase;
}

h1 span {
  display: block;
  white-space: nowrap;
}

h1 .title-course {
  color: var(--blue);
  text-shadow: 0 0 32px rgba(107, 188, 255, .16);
}

h1 .title-subject { color: var(--text); }

h2 {
  margin-bottom: 8px;
  font-size: clamp(2.3rem, 4.8vw, 4.7rem);
  line-height: .92;
  text-transform: uppercase;
}

h3 {
  margin-bottom: 8px;
  font-size: 1.25rem;
  line-height: 1.15;
}

p { color: var(--muted); }

.eyebrow {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 0 0 13px;
  color: var(--green);
  font: 500 .69rem/1.4 var(--font-mono);
  letter-spacing: .09em;
  text-transform: uppercase;
}

.eyebrow span { color: var(--yellow); }

.course-intro {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(320px, .75fr);
  gap: clamp(45px, 7vw, 105px);
  min-height: calc(100svh - 86px);
  align-items: center;
  padding: 76px 24px 100px;
  background: radial-gradient(circle at 78% 43%, rgba(97, 227, 165, .07), transparent 34%);
}

.course-intro::after {
  position: absolute;
  right: 0;
  bottom: 0;
  left: 0;
  height: 12px;
  background: linear-gradient(to right, var(--green) 0 33.333%, var(--blue) 33.333% 66.666%, var(--yellow) 66.666% 100%);
  content: "";
}

.intro-copy {
  min-width: 0;
  overflow-wrap: break-word;
}

.lead {
  max-width: 760px;
  margin-bottom: 13px;
  color: #d5dde2;
  font-size: clamp(1rem, 1.5vw, 1.16rem);
  line-height: 1.55;
}

.teacher-line {
  max-width: 740px;
  margin-bottom: 27px;
  font-size: .9rem;
}

.teacher-line strong { color: var(--text); }

.intro-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 40px;
}

.button {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  padding: 10px 14px;
  border: 1px solid var(--line-strong);
  border-radius: 9px;
  color: var(--text);
  background: rgba(244, 247, 248, .025);
  font-size: .82rem;
  font-weight: 700;
  text-decoration: none;
  transition: border-color .2s ease, background .2s ease, transform .2s ease;
}

.button::after {
  margin-left: 9px;
  content: "→";
}

.button.primary {
  border-color: var(--green);
  color: var(--ink);
  background: var(--green);
}

.button.guide-download {
  border-color: var(--yellow);
  color: var(--ink);
  background: var(--yellow);
  box-shadow: 0 0 24px rgba(255, 209, 102, .12);
}

.button.guide-download::after { content: "↓"; }

.button.guide-download:hover,
.button.guide-download:focus-visible {
  border-color: #ffe29a;
  background: #ffe29a;
}

.button:hover,
.button:focus-visible {
  border-color: var(--blue);
  transform: translateY(-2px);
}

.course-facts {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
  max-width: 760px;
}

.course-facts span {
  padding-top: 12px;
  border-top: 1px solid var(--line-strong);
  color: var(--muted);
  font: 400 .64rem/1.4 var(--font-mono);
  letter-spacing: .03em;
  text-transform: uppercase;
}

.course-facts strong {
  display: block;
  margin-bottom: 7px;
  color: var(--text);
  font: 700 clamp(1.15rem, 2.2vw, 1.8rem)/1 var(--font-display);
  letter-spacing: -.05em;
  text-transform: none;
}

.course-visual {
  position: relative;
  min-width: 0;
  margin: 0 28px 28px 0;
  overflow: hidden;
  border: 1px solid rgba(244, 247, 248, .2);
  border-radius: 18px;
  background: #0a0f12;
  box-shadow: 10px 10px 0 #2ca977, 20px 20px 0 #287cb5, 30px 30px 0 #d3a62d;
}

.visual-toolbar {
  display: flex;
  min-height: 42px;
  align-items: center;
  gap: 7px;
  padding: 0 14px;
  border-bottom: 1px solid var(--line);
  background: var(--surface);
}

.visual-toolbar span {
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--red);
}

.visual-toolbar span:nth-child(2) { background: var(--yellow); }
.visual-toolbar span:nth-child(3) { background: var(--green); }

.visual-toolbar code {
  margin-left: auto;
  color: var(--muted);
  font: 400 .65rem/1 var(--font-mono);
}

.terminal-window {
  display: flex;
  height: 400px;
  min-height: 400px;
  flex-direction: column;
  padding: 15px 17px 13px;
  background:
    linear-gradient(rgba(97, 227, 165, .028) 1px, transparent 1px),
    linear-gradient(90deg, rgba(97, 227, 165, .028) 1px, transparent 1px),
    #080d10;
  background-size: 18px 18px;
  font-family: var(--font-mono);
}

.terminal-command {
  margin: 0 0 14px;
  color: #d4dee3;
  font: 400 .66rem/1.5 var(--font-mono);
}

.terminal-command span { color: var(--green); }
.terminal-command strong { color: var(--blue); font-weight: 500; }

.terminal-editor {
  height: 260px;
  min-height: 260px;
  flex: 0 0 260px;
  margin: 0;
  overflow: hidden;
  color: #e2ebef;
  font: 400 clamp(.67rem, 1vw, .78rem)/1.65 var(--font-mono);
  white-space: pre-wrap;
}

.terminal-editor code { font: inherit; }

.py-keyword { color: #c792ea; }
.py-function { color: var(--green); }
.py-type { color: var(--red); }
.py-string { color: var(--yellow); }
.py-docstring { color: #8fa8e8; font-style: italic; }
.py-operator { color: var(--blue); }
.py-punctuation { color: #dce6eb; }
.py-comment { color: #71828c; font-style: italic; }

.terminal-cursor {
  display: inline-block;
  width: 7px;
  height: 1.12em;
  margin-left: 2px;
  vertical-align: -.16em;
  background: var(--green);
  box-shadow: 0 0 10px rgba(97, 227, 165, .55);
  animation: terminal-blink .8s steps(1) infinite;
}

.terminal-result {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 2px 12px;
  align-items: center;
  margin-top: auto;
  padding-top: 11px;
  border-top: 1px solid var(--line);
  opacity: 0;
  transform: translateY(5px);
  transition: opacity .25s ease, transform .25s ease;
}

.terminal-result.is-visible {
  opacity: 1;
  transform: translateY(0);
}

.terminal-result span {
  color: var(--muted);
  font-size: .63rem;
}

.terminal-result strong {
  grid-row: span 2;
  padding: 5px 9px;
  border: 1px solid var(--green);
  border-radius: 999px;
  color: var(--green);
  background: rgba(97, 227, 165, .08);
  font-size: .68rem;
  font-weight: 500;
}

.terminal-result small {
  color: var(--blue);
  font-size: .54rem;
}

.visually-hidden {
  position: absolute !important;
  width: 1px !important;
  height: 1px !important;
  padding: 0 !important;
  overflow: hidden !important;
  clip: rect(0, 0, 0, 0) !important;
  white-space: nowrap !important;
  border: 0 !important;
}

@keyframes terminal-blink {
  0%, 48% { opacity: 1; }
  49%, 100% { opacity: 0; }
}

.course-visual figcaption {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 12px 15px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: .72rem;
}

.course-visual figcaption code {
  color: var(--green);
  font-family: var(--font-mono);
}

.page-section {
  position: relative;
  padding: 94px 24px;
  border-bottom: 1px solid var(--line);
  scroll-margin-top: 90px;
}

.page-section::before {
  position: absolute;
  z-index: -1;
  top: 70px;
  right: 22px;
  color: rgba(244, 247, 248, .055);
  content: attr(data-index);
  font-size: clamp(5rem, 12vw, 10rem);
  font-weight: 700;
  letter-spacing: -.1em;
  line-height: .65;
  pointer-events: none;
}

.section-heading {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 34px;
  margin-bottom: 36px;
}

.section-heading > p {
  max-width: 480px;
  margin-bottom: 2px;
  font-size: .92rem;
}

.module-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
}

.module-card {
  position: relative;
  display: flex;
  min-width: 0;
  min-height: 286px;
  flex-direction: column;
  padding: 21px;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 14px;
  color: var(--text);
  background: linear-gradient(145deg, var(--surface-2), var(--surface));
  text-decoration: none;
  transition: border-color .2s ease, transform .2s ease, box-shadow .2s ease;
}

.module-card::before {
  position: absolute;
  top: 0;
  right: 0;
  left: 0;
  height: 3px;
  background: var(--module-color);
  content: "";
}

.module-card:hover,
.module-card:focus-visible {
  border-color: var(--module-color);
  box-shadow: 0 16px 34px rgba(0, 0, 0, .23);
  transform: translateY(-5px);
}

.module-python { --module-color: var(--green); }
.module-structures { --module-color: var(--blue); }
.module-strings { --module-color: var(--red); }
.module-graphs { --module-color: #65d4d0; }
.module-geometry { --module-color: var(--yellow); }
.module-paradigms { --module-color: var(--purple); }

.module-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 28px;
  color: var(--muted);
  font: 400 .65rem/1.3 var(--font-mono);
  text-transform: uppercase;
}

.module-number {
  display: grid;
  width: 38px;
  height: 32px;
  place-items: center;
  border: 1px solid color-mix(in srgb, var(--module-color) 65%, transparent);
  border-radius: 8px;
  color: var(--module-color);
  background: color-mix(in srgb, var(--module-color) 10%, transparent);
  font-weight: 500;
}

.module-card h3 { font-size: 1.35rem; }

.module-card p {
  margin-bottom: 17px;
  font-size: .86rem;
}

.module-topics {
  margin-bottom: 18px;
  color: var(--module-color);
  font: 500 .64rem/1.5 var(--font-mono);
  text-transform: uppercase;
}

.module-action {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: auto;
  padding-top: 15px;
  border-top: 1px solid var(--line);
  font-size: .8rem;
}

.module-action::after { color: var(--module-color); content: "↗"; }

.video-section,
.study-method {
  width: 100vw;
  margin-left: calc(50% - 50vw);
  padding-right: max(24px, calc((100vw - var(--content)) / 2 + 24px));
  padding-left: max(24px, calc((100vw - var(--content)) / 2 + 24px));
  background: rgba(21, 28, 32, .66);
}

.study-method { background: rgba(16, 23, 27, .82); }

.video-playlist {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 360px;
  gap: 16px;
  align-items: start;
}

.playlist-player,
.playlist-panel {
  min-width: 0;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 13px;
  background: var(--surface);
}

.playlist-player {
  box-shadow: 0 20px 44px rgba(0, 0, 0, .2);
}

.video-frame {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background: #080d10;
}

.video-frame iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

.video-info {
  display: flex;
  min-height: 88px;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  padding: 14px 16px;
}

.video-info span {
  display: block;
  margin-bottom: 3px;
  color: var(--green);
  font: 500 .61rem/1.4 var(--font-mono);
  letter-spacing: .06em;
  text-transform: uppercase;
}

.video-info h3 {
  margin: 0;
  font-size: 1rem;
  letter-spacing: -.025em;
}

.video-info a {
  flex: 0 0 auto;
  color: var(--blue);
  font-size: .72rem;
  font-weight: 700;
  text-decoration: none;
}

.video-info a:hover { text-decoration: underline; }

.playlist-now-playing {
  border-top: 1px solid var(--line);
}

.playlist-panel {
  display: flex;
  height: 550px;
  flex-direction: column;
  overflow: visible;
  border: 0;
  background: transparent;
}

.playlist-header {
  display: flex;
  min-height: 64px;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 11px;
  padding: 11px 14px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface-2);
}

.playlist-header span,
.playlist-copy small {
  display: block;
  color: var(--green);
  font: 500 .61rem/1.4 var(--font-mono);
  letter-spacing: .06em;
  text-transform: uppercase;
}

.playlist-header strong {
  display: block;
  margin-top: 3px;
  color: var(--text);
  font-size: 1rem;
}

.playlist-header > small {
  padding: 5px 8px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  color: var(--muted);
  font: 400 .62rem/1 var(--font-mono);
  white-space: nowrap;
}

.playlist-list {
  display: grid;
  min-height: 0;
  gap: 10px;
  margin: 0;
  padding: 0 5px 0 0;
  overflow-y: auto;
  list-style: none;
  scrollbar-color: var(--line-strong) var(--surface);
  scrollbar-width: thin;
}

.playlist-list li { min-width: 0; }

.playlist-item {
  --thumb-color: var(--green);
  position: relative;
  display: grid;
  width: 100%;
  min-height: 72px;
  grid-template-columns: 128px minmax(0, 1fr);
  gap: 10px;
  align-items: center;
  padding: 0;
  border: 1px solid transparent;
  border-radius: 10px;
  color: var(--text);
  background: transparent;
  font: inherit;
  text-align: left;
  cursor: pointer;
  transition: background .18s ease, border-color .18s ease;
}

.playlist-list li:nth-child(2) .playlist-item { --thumb-color: var(--blue); }
.playlist-list li:nth-child(3) .playlist-item { --thumb-color: var(--yellow); }
.playlist-list li:nth-child(4) .playlist-item { --thumb-color: var(--red); }
.playlist-list li:nth-child(5) .playlist-item { --thumb-color: #65d4d0; }
.playlist-list li:nth-child(6) .playlist-item { --thumb-color: var(--purple); }
.playlist-list li:nth-child(7) .playlist-item { --thumb-color: var(--green); }

.playlist-item:hover {
  border-color: var(--line);
  background: var(--surface-2);
}

.playlist-item.is-active {
  border-color: var(--green);
  background: #14231d;
}

.playlist-index {
  position: relative;
  display: grid;
  width: 128px;
  height: 72px;
  overflow: hidden;
  place-items: center;
  border: 1px solid color-mix(in srgb, var(--thumb-color) 42%, var(--line));
  border-radius: 8px;
  color: color-mix(in srgb, var(--thumb-color) 80%, white);
  background:
    linear-gradient(rgba(255, 255, 255, .035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, .035) 1px, transparent 1px),
    linear-gradient(135deg, color-mix(in srgb, var(--thumb-color) 22%, #0b1114), #0b1114 68%);
  background-size: 16px 16px, 16px 16px, auto;
  font: 500 1.15rem/1 var(--font-mono);
}

.playlist-index::before {
  position: absolute;
  top: 7px;
  left: 8px;
  color: color-mix(in srgb, var(--thumb-color) 75%, white);
  content: "VIDEOAULA";
  font: 500 .42rem/1 var(--font-mono);
  letter-spacing: .08em;
}

.playlist-index::after {
  position: absolute;
  right: -13px;
  bottom: -27px;
  width: 74px;
  height: 74px;
  border: 1px solid color-mix(in srgb, var(--thumb-color) 50%, transparent);
  border-radius: 50%;
  content: "";
}

.playlist-copy {
  min-width: 0;
}

.playlist-copy strong {
  display: block;
  margin-top: 3px;
  color: var(--text);
  font-size: .83rem;
  line-height: 1.25;
  display: -webkit-box;
  overflow: hidden;
  -webkit-box-orient: vertical;
  -webkit-line-clamp: 2;
}

.playlist-play {
  position: absolute;
  z-index: 2;
  top: 22px;
  left: 50px;
  display: grid;
  width: 28px;
  height: 28px;
  place-items: center;
  border: 1px solid var(--line-strong);
  border-radius: 50%;
  color: var(--text);
  background: rgba(8, 12, 14, .78);
  font-size: .55rem;
  opacity: 0;
  transform: scale(.85);
  transition: opacity .18s ease, transform .18s ease;
}

.playlist-item.is-active .playlist-index,
.playlist-item.is-active .playlist-play { color: var(--green); }

.playlist-item:hover .playlist-play,
.playlist-item.is-active .playlist-play {
  opacity: 1;
  transform: scale(1);
}

.playlist-item.is-active .playlist-play {
  border-color: var(--green);
  background: rgba(12, 17, 20, .9);
}

.method-steps {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.method-steps li {
  min-width: 0;
  padding: 19px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
}

.method-steps li > span {
  display: grid;
  width: 34px;
  height: 34px;
  margin-bottom: 25px;
  place-items: center;
  border: 1px solid #4a725f;
  border-radius: 9px;
  color: var(--green);
  background: #143426;
  font: 500 .72rem/1 var(--font-mono);
}

.method-steps strong {
  display: block;
  margin-bottom: 6px;
  color: var(--text);
}

.method-steps p {
  margin: 0;
  font-size: .82rem;
}

.source-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
}

.source-grid a {
  display: flex;
  min-width: 0;
  min-height: 164px;
  flex-direction: column;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
  text-decoration: none;
  transition: border-color .2s ease, background .2s ease;
}

.source-grid a:hover,
.source-grid a:focus-visible {
  border-color: var(--blue);
  background: var(--surface-2);
}

.source-grid strong { margin-bottom: 6px; }
.source-grid span { color: var(--muted); font-size: .82rem; }

.source-grid small {
  margin-top: auto;
  padding-top: 14px;
  color: var(--blue);
  font: 500 .62rem/1.4 var(--font-mono);
  text-transform: uppercase;
}

.professor-section {
  display: grid;
  grid-template-columns: minmax(280px, .9fr) minmax(0, 1.1fr);
  gap: 64px;
  align-items: start;
  border-bottom: 0;
}

.professor-section p:last-child {
  margin: 7px 0 0;
  padding: 20px 0 20px 22px;
  border-left: 3px solid var(--green);
  font-size: 1rem;
}

.site-footer {
  border-top: 1px solid var(--line);
  background: #080c0e;
}

.footer-inner {
  display: flex;
  min-height: 130px;
  align-items: center;
  justify-content: space-between;
  gap: 40px;
  padding: 26px 0;
  color: var(--muted);
  font-size: .76rem;
}

.footer-inner > span:first-child,
.footer-inner > span:first-child strong,
.footer-inner > span:first-child small { display: block; }

.footer-inner > span:first-child strong {
  color: var(--green);
  font-family: var(--font-mono);
  font-size: .8rem;
}

.footer-inner > span:first-child small { margin-top: 5px; color: var(--muted); }
.footer-inner > span:last-child { max-width: 690px; text-align: right; }

@media (max-width: 1050px) {
  .course-intro { grid-template-columns: minmax(0, 1.15fr) minmax(300px, .85fr); gap: 45px; }
  h1 { font-size: clamp(2.8rem, 4.9vw, 4.2rem); }
  .module-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .video-playlist { grid-template-columns: minmax(0, 1fr) 330px; }
}

@media (max-width: 820px) {
  .site-header { padding: 12px 14px 0; }
  .topbar { align-items: flex-start; flex-direction: column; gap: 10px; padding: 12px 14px; }
  .topnav { width: 100%; justify-content: flex-start; }
  .course-intro { grid-template-columns: minmax(0, 1fr); min-height: 0; padding-top: 68px; }
  .course-visual { max-width: 560px; }
  .section-heading { align-items: flex-start; flex-direction: column; gap: 10px; }
  .video-playlist { grid-template-columns: minmax(0, 1fr); }
  .playlist-panel { height: auto; max-height: 480px; }
  .method-steps { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .professor-section { grid-template-columns: 1fr; gap: 24px; }
}

@media (max-width: 620px) {
  .topbar,
  main,
  .footer-inner { width: min(100% - 28px, var(--content)); }
  .topnav { gap: 8px 14px; }
  .topnav a { font-size: .72rem; }
  .topnav .nav-profile { padding: 7px 9px; }
  .course-intro { gap: 40px; padding: 54px 4px 84px; }
  h1 { font-size: clamp(2rem, 8.8vw, 2.8rem); }
  h2 { font-size: clamp(2.15rem, 12vw, 3.35rem); }
  .course-facts { grid-template-columns: 1fr; gap: 10px; }
  .course-facts span { display: grid; grid-template-columns: 110px 1fr; align-items: center; }
  .course-facts strong { margin: 0; }
  .course-visual { margin-right: 22px; }
  .course-visual img { min-height: 220px; }
  .course-visual figcaption { align-items: flex-start; flex-direction: column; gap: 4px; }
  .page-section { padding: 72px 4px; }
  .video-section,
  .study-method { padding-right: 18px; padding-left: 18px; }
  .module-grid,
  .method-steps,
  .source-grid { grid-template-columns: 1fr; }
  .module-card { min-height: 255px; }
  .playlist-item { grid-template-columns: 112px minmax(0, 1fr); }
  .playlist-index { width: 112px; height: 63px; }
  .playlist-play { top: 18px; left: 42px; }
  .page-section::before { top: 54px; right: 5px; }
  .footer-inner { align-items: flex-start; flex-direction: column; gap: 20px; }
  .footer-inner > span:last-child { text-align: left; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition: none !important; }
  .terminal-cursor { animation: none; }
  .module-card:hover,
  .button:hover { transform: none; }
}