@import url('https://fonts.googleapis.com/css2?family=Hind+Siliguri:wght@300;400;500;600;700&family=Inter:wght@400;500;600;700;800&family=Playfair+Display:wght@600;700;800&family=JetBrains+Mono:wght@400;600&display=swap');

:root {
  --course-cream: #FAF8F4;
  --course-cream2: #F2EDE4;
  --course-navy: #0C2340;
  --course-navy2: #132F52;
  --course-teal: #0F6E56;
  --course-teal-lt: #E1F5EE;
  --course-gold: #B8860B;
  --course-gold-lt: #FEF6E4;
  --course-white: #FFFFFF;
  --course-text: #1A1A18;
  --course-text2: #4A4A46;
  --course-text3: #7A7A74;
  --course-border: rgba(12, 35, 64, 0.10);
  --course-shadow: 0 4px 24px rgba(12, 35, 64, 0.08);
  --course-shadow-lg: 0 12px 40px rgba(12, 35, 64, 0.12);
  --course-radius: 14px;
  --course-radius-sm: 10px;
  --course-font: 'Hind Siliguri', sans-serif;
  --course-serif: 'Playfair Display', Georgia, serif;
  --course-mono: 'JetBrains Mono', monospace;
  --course-topbar-h: 56px;
  --course-footer-nav-h: 64px;
  --course-sticky-nav-h: 52px;
  --course-fab-btn-h: 2.75rem;
  --course-fab-btn-min-w: 7.5rem;
  --course-fab-stack-gap: 0.75rem;
}

[data-theme="light"] {
  --rm-bg: #FAF8F4;
  --rm-surface: #FFFFFF;
  --rm-surface2: #F2EDE4;
  --rm-border: rgba(12, 35, 64, 0.12);
  --rm-text: #1A1A18;
  --rm-muted: #7A7A74;
  --rm-accent: #0F6E56;
  --rm-done: #0F6E56;
  --rm-node-teal: #0B6049;
  --rm-node-blue: #185FA5;
  --rm-node-amber: #9A6700;
  --rm-node-purple: #6E40C9;
  --rm-node-rose: #BF3989;
  --rm-node-green: #0B6049;
  --rm-topbar-bg: rgba(250, 248, 244, 0.95);
  --rm-topbar-text: #0C2340;
  --rm-topbar-border: rgba(12, 35, 64, 0.12);
  --rm-topbar-btn-bg: rgba(12, 35, 64, 0.06);
  --rm-topbar-btn-border: rgba(12, 35, 64, 0.15);
  --rm-topbar-btn-hover: rgba(12, 35, 64, 0.1);
  --rm-footer-bg: rgba(255, 255, 255, 0.96);
  --rm-node-shadow: 0 8px 24px rgba(12, 35, 64, 0.1);
  --rm-progress-track: rgba(12, 35, 64, 0.1);
}

[data-theme="dark"] {
  --rm-bg: #0d1117;
  --rm-surface: #161b22;
  --rm-surface2: #21262d;
  --rm-border: #30363d;
  --rm-text: #e6edf3;
  --rm-muted: #8b949e;
  --rm-accent: #58a6ff;
  --rm-done: #3fb950;
  --rm-node-teal: #3fb950;
  --rm-node-blue: #58a6ff;
  --rm-node-amber: #d29922;
  --rm-node-purple: #bc8cff;
  --rm-node-rose: #f778ba;
  --rm-node-green: #3fb950;
  --rm-topbar-bg: rgba(13, 17, 23, 0.95);
  --rm-topbar-text: #e6edf3;
  --rm-topbar-border: #30363d;
  --rm-topbar-btn-bg: rgba(255, 255, 255, 0.06);
  --rm-topbar-btn-border: rgba(255, 255, 255, 0.15);
  --rm-topbar-btn-hover: rgba(255, 255, 255, 0.14);
  --rm-footer-bg: rgba(22, 27, 34, 0.98);
  --rm-node-shadow: 0 8px 24px rgba(0, 0, 0, 0.35);
  --rm-progress-track: rgba(255, 255, 255, 0.08);
}

/* Hide document scrollbar; scroll via wheel/touch/keyboard still works */
html {
  scrollbar-width: none;
  -ms-overflow-style: none;
}

html::-webkit-scrollbar {
  width: 0;
  height: 0;
  display: none;
}

/* ── Course shell (lecture pages) ── */
body.course-page {
  padding-top: calc(var(--course-topbar-h) + env(safe-area-inset-top, 0px));
  padding-bottom: calc(var(--course-footer-nav-h) + env(safe-area-inset-bottom, 0px));
}

body.course-page.has-sticky-part-nav {
  padding-bottom: calc(
    var(--course-footer-nav-h) + var(--course-sticky-nav-h) +
    env(safe-area-inset-bottom, 0px)
  );
}

@media (min-width: 901px) {
  body.course-page.has-sticky-part-nav {
    padding-bottom: calc(var(--course-sticky-nav-h) + env(safe-area-inset-bottom, 0px));
  }
}

body.course-page.has-drawer-nav {
  padding-bottom: calc(var(--course-footer-nav-h) + env(safe-area-inset-bottom, 0px));
}

/* ── Topbar ── */
.course-topbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 9000;
  height: var(--course-topbar-h);
  padding-top: env(safe-area-inset-top, 0px);
  background: var(--rm-topbar-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--rm-topbar-border);
  color: var(--rm-topbar-text);
}

.course-topbar-inner {
  max-width: 1200px;
  margin: 0 auto;
  height: var(--course-topbar-h);
  padding: 0 1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.course-topbar-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.35rem;
  min-height: 40px;
  min-width: 40px;
  padding: 0.4rem 0.75rem;
  border: 1px solid var(--rm-topbar-btn-border);
  border-radius: 8px;
  background: var(--rm-topbar-btn-bg);
  color: var(--rm-topbar-text);
  font-family: var(--course-font);
  font-size: 0.82rem;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
  white-space: nowrap;
}

.course-topbar-btn:hover {
  background: var(--rm-topbar-btn-hover);
  border-color: var(--rm-accent);
}

.course-topbar-btn:disabled,
.course-topbar-btn.is-disabled {
  opacity: 0.35;
  pointer-events: none;
}

.course-topbar-btn.accent {
  background: var(--course-teal);
  border-color: var(--course-teal);
}

.course-topbar-btn.accent:hover {
  background: #0d8064;
}

.course-topbar-center {
  flex: 1;
  text-align: center;
  min-width: 0;
  padding: 0 0.5rem;
}

.course-topbar-label {
  display: block;
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  opacity: 0.65;
  line-height: 1.2;
}

.course-topbar-title {
  display: block;
  font-size: 0.88rem;
  font-weight: 600;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

/* ── YC lecture topbar (hub-matched) ── */
body.course-page--yc {
  --course-topbar-h: 64px;
}

.course-topbar--yc {
  background: rgba(250, 248, 244, 0.88);
  border-bottom: 1px solid var(--rm-border);
  box-shadow: none;
}

[data-theme="dark"] .course-topbar--yc {
  background: rgba(13, 17, 23, 0.9);
  border-bottom-color: var(--rm-border);
}

.course-topbar--yc .course-topbar-inner {
  max-width: 1100px;
  padding: 0 1.25rem;
  justify-content: space-between;
  gap: 1rem;
}

.course-topbar-start {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  min-width: 0;
  flex: 1;
}

.course-topbar-menu {
  display: none;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  padding: 0;
  border: 1px solid var(--rm-topbar-btn-border);
  border-radius: 10px;
  background: var(--rm-topbar-btn-bg);
  color: var(--rm-topbar-text);
  cursor: pointer;
  flex-shrink: 0;
  transition: background 0.15s, border-color 0.15s;
}

.course-topbar-menu:hover {
  background: var(--rm-topbar-btn-hover);
  border-color: var(--course-teal);
}

.course-topbar-brand {
  display: flex;
  align-items: center;
  text-decoration: none;
  flex-shrink: 0;
}

.course-topbar-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 8px;
  background: linear-gradient(145deg, var(--course-teal), #0d5c47);
  color: #fff;
  font-family: 'Inter', 'Hind Siliguri', system-ui, sans-serif;
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  box-shadow: 0 2px 10px rgba(15, 110, 86, 0.35);
  transition: transform 0.15s, box-shadow 0.15s;
}

.course-topbar-brand:hover .course-topbar-mark {
  transform: translateY(-1px);
  box-shadow: 0 4px 14px rgba(15, 110, 86, 0.45);
}

.course-topbar-module {
  min-width: 0;
  padding-left: 0.15rem;
  border-left: 1px solid var(--rm-border);
  margin-left: 0.15rem;
  padding-left: 0.85rem;
}

.course-topbar--yc .course-topbar-label {
  font-family: 'Inter', 'Hind Siliguri', system-ui, sans-serif;
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--course-teal);
  opacity: 1;
}

.course-topbar--yc .course-topbar-title {
  font-family: 'Inter', 'Hind Siliguri', system-ui, sans-serif;
  font-size: 0.92rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--rm-text);
}

.course-topbar-actions {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  flex-shrink: 0;
}

.course-topbar-nav {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.3rem;
  border-radius: 999px;
  border: 1px solid var(--rm-border);
  background: var(--rm-topbar-btn-bg);
}

.course-topbar-nav-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.3rem;
  min-height: 36px;
  padding: 0.35rem 0.85rem;
  border: none;
  border-radius: 999px;
  background: transparent;
  color: var(--rm-text);
  font-family: 'Inter', 'Hind Siliguri', system-ui, sans-serif;
  font-size: 0.8rem;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  white-space: nowrap;
  transition: background 0.15s, color 0.15s;
}

.course-topbar-nav-btn:hover {
  background: var(--rm-surface);
  color: var(--course-teal);
}

.course-topbar-nav-btn--next {
  background: var(--course-teal);
  color: #fff;
}

.course-topbar-nav-btn--next:hover {
  background: #0d8064;
  color: #fff;
}

.course-topbar-nav-btn.is-disabled {
  opacity: 0.35;
  pointer-events: none;
}

.course-topbar-utils {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.3rem;
  border-radius: 999px;
  border: 1px solid var(--rm-border);
  background: var(--rm-topbar-btn-bg);
}

.course-topbar--yc .course-theme-toggle--nav {
  min-width: 40px;
  min-height: 40px;
  padding: 0;
  border: 1px solid var(--rm-topbar-btn-border) !important;
  border-radius: 999px;
  background: var(--rm-surface) !important;
  color: var(--rm-text);
  box-shadow: 0 1px 3px rgba(12, 35, 64, 0.08);
}

.course-topbar--yc .course-theme-toggle--nav:hover {
  background: var(--rm-topbar-btn-hover) !important;
  border-color: var(--rm-accent) !important;
  color: var(--rm-accent);
}

/* ── YC footer nav ── */
.course-footer-nav--yc {
  background: rgba(250, 248, 244, 0.92);
  border-top: 1px solid var(--rm-border);
  box-shadow: none;
}

[data-theme="dark"] .course-footer-nav--yc {
  background: rgba(13, 17, 23, 0.92);
}

.course-footer-nav--yc .course-footer-nav-inner {
  max-width: 1100px;
  gap: 0.5rem;
}

.course-footer-nav--yc .course-footer-btn {
  flex: 1;
  border-radius: 999px;
  border-color: var(--rm-border);
  background: var(--rm-surface);
  font-family: 'Inter', 'Hind Siliguri', system-ui, sans-serif;
  font-size: 0.8rem;
  font-weight: 600;
  gap: 0.4rem;
  min-height: 42px;
}

.course-footer-nav--yc .course-footer-btn .footer-label {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.course-footer-nav--yc .course-footer-btn:hover {
  border-color: var(--course-teal);
  background: var(--rm-surface2);
}

.course-footer-nav--yc .course-footer-btn--hub {
  flex: 0 0 auto;
  min-width: 72px;
  background: var(--course-teal);
  border-color: var(--course-teal);
  color: #fff;
}

.course-footer-nav--yc .course-footer-btn--hub:hover {
  background: #0d8064;
  border-color: #0d8064;
  color: #fff;
}

.course-footer-nav--yc .course-footer-btn--next {
  color: var(--course-teal);
  border-color: rgba(15, 110, 86, 0.25);
  background: var(--course-teal-lt);
}

.course-footer-nav--yc .course-footer-btn--next:hover {
  background: var(--course-teal);
  color: #fff;
  border-color: var(--course-teal);
}

.course-progress-wrap {
  position: fixed;
  top: calc(var(--course-topbar-h) + env(safe-area-inset-top, 0px));
  left: 0;
  right: 0;
  height: 3px;
  z-index: 8999;
  background: var(--rm-progress-track);
}

.course-progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--rm-node-teal), var(--rm-accent));
  transition: width 0.3s ease;
  width: 0%;
}

/* ── Footer nav (mobile-first, visible all sizes) ── */
.course-footer-nav {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  z-index: 9000;
  height: var(--course-footer-nav-h);
  padding-bottom: env(safe-area-inset-bottom, 0px);
  background: var(--rm-footer-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-top: 1px solid var(--rm-border);
  box-shadow: 0 -4px 20px rgba(12, 35, 64, 0.06);
}

.course-footer-nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  height: 100%;
  padding: 0 0.75rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
}

.course-footer-btn {
  flex: 1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.35rem;
  min-height: 44px;
  padding: 0.5rem 0.75rem;
  border-radius: var(--course-radius-sm);
  border: 1px solid var(--rm-border);
  background: var(--rm-surface);
  color: var(--rm-text);
  font-family: var(--course-font);
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: none;
  transition: background 0.15s, border-color 0.15s;
}

.course-footer-btn:hover {
  background: var(--rm-surface2);
  border-color: var(--rm-accent);
}

.course-footer-btn.primary {
  background: var(--rm-accent);
  color: #fff;
  border-color: var(--rm-accent);
}

.course-footer-btn.primary:hover {
  filter: brightness(1.08);
}

.course-footer-btn:disabled,
.course-footer-btn.is-disabled {
  opacity: 0.35;
  pointer-events: none;
}

/* ── Mobile drawer toggle ── */
.course-drawer-toggle {
  display: none;
}

.course-drawer-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(12, 35, 64, 0.5);
  z-index: 8500;
  opacity: 0;
  transition: opacity 0.25s;
}

.course-drawer-overlay.is-open {
  display: block;
  opacity: 1;
}

body.course-page .sticky-nav {
  top: auto;
  bottom: var(--course-footer-nav-h);
  z-index: 8000;
}

@media (min-width: 901px) {
  body.course-page .sticky-nav {
    bottom: 0;
  }
}

body.course-page.has-sticky-part-nav .glossary-fab {
  bottom: calc(var(--course-footer-nav-h) + var(--course-sticky-nav-h) + 1rem);
}

@media (min-width: 901px) {
  body.course-page.has-sticky-part-nav .glossary-fab {
    bottom: calc(var(--course-sticky-nav-h) + 1rem);
  }
}

/* Desktop: hide mobile-only section drawer (incl. course.js-injected #course-toc-drawer) */
@media (min-width: 901px) {
  #sidebar.course-toc-drawer,
  #course-toc-drawer,
  .course-toc-drawer {
    display: none !important;
  }
}

@media (max-width: 900px) {
  .course-drawer-toggle {
    display: inline-flex;
  }

  body.course-page .course-toc-drawer,
  body.course-page #course-toc-drawer,
  body.course-page #sidebar.course-toc-drawer {
    background: var(--course-navy);
    color: #fff;
    padding: 1rem 1.25rem;
    border-right: 1px solid rgba(255, 255, 255, 0.1);
  }

  body.course-page--yc .course-toc-drawer,
  body.course-page--yc #course-toc-drawer,
  body.course-page--yc #sidebar.course-toc-drawer {
    background: var(--rm-surface) !important;
    color: var(--rm-text) !important;
    border-right: 1px solid var(--rm-border) !important;
  }

  body.course-page--yc .course-drawer-link {
    color: var(--rm-muted) !important;
    border-bottom-color: var(--rm-border) !important;
  }

  body.course-page--yc .course-drawer-link:hover {
    color: var(--rm-text) !important;
    background: var(--rm-surface2);
  }

  .course-drawer-title {
    font-size: 0.72rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    opacity: 0.6;
    margin-bottom: 1rem;
  }

  .course-drawer-link {
    display: block;
    padding: 0.45rem 0;
    color: rgba(255, 255, 255, 0.88);
    text-decoration: none;
    font-size: 0.88rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.06);
  }

  .course-drawer-link:hover {
    color: #fff;
  }

  body.course-page #sidebar.course-toc-drawer,
  body.course-page .course-toc-drawer,
  body.course-page #course-toc-drawer {
    position: fixed !important;
    top: calc(var(--course-topbar-h) + env(safe-area-inset-top, 0px)) !important;
    left: 0 !important;
    bottom: calc(var(--course-footer-nav-h) + env(safe-area-inset-bottom, 0px)) !important;
    width: min(300px, 88vw) !important;
    max-width: 88vw !important;
    z-index: 8600 !important;
    transform: translateX(-110%) !important;
    transition: transform 0.28s ease !important;
    margin: 0 !important;
    overflow-y: auto !important;
    box-shadow: var(--course-shadow-lg) !important;
  }

  body.course-page #sidebar.course-toc-drawer.course-drawer-open,
  body.course-page .course-toc-drawer.course-drawer-open,
  body.course-page #course-toc-drawer.course-drawer-open {
    transform: translateX(0) !important;
  }

  body.course-page.has-drawer-nav .toc-wrapper,
  body.course-page.has-drawer-nav .lr-toc {
    display: none;
  }

  body.course-page #main {
    margin-left: 0 !important;
  }
}

/* ── Homepage (roadmap.sh dark) ── */
.course-hub {
  font-family: var(--course-font);
  background: var(--rm-bg);
  color: var(--rm-text);
  min-height: 100vh;
  line-height: 1.65;
}

.course-hub-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  width: 100%;
  background: rgba(10, 12, 20, 0.62);
  backdrop-filter: blur(18px) saturate(1.4);
  -webkit-backdrop-filter: blur(18px) saturate(1.4);
  border-bottom: 1px solid rgba(255, 255, 255, 0.07);
  box-shadow: 0 1px 0 rgba(255, 255, 255, 0.04) inset;
}

[data-theme="light"] .course-hub-nav {
  background: rgba(255, 255, 255, 0.72);
  border-bottom-color: rgba(15, 23, 42, 0.07);
  box-shadow: 0 1px 0 rgba(255, 255, 255, 0.8) inset;
}

.course-hub-nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  min-height: 64px;
  padding: 0 1.75rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.25rem;
}

.course-hub-nav-brand {
  display: flex;
  align-items: center;
  text-decoration: none;
  flex-shrink: 0;
}

.course-hub-nav-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  border-radius: 11px;
  background: linear-gradient(145deg, var(--course-teal), #0d5c47);
  color: #fff;
  font-family: var(--course-font);
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  box-shadow: 0 2px 10px rgba(15, 110, 86, 0.35);
  transition: transform 0.15s, box-shadow 0.15s;
}

.course-hub-nav-brand:hover .course-hub-nav-mark {
  transform: translateY(-1px);
  box-shadow: 0 4px 14px rgba(15, 110, 86, 0.45);
}

.course-hub-nav-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-shrink: 0;
  padding: 0.35rem;
  border-radius: 999px;
  border: 1px solid var(--rm-border);
  background: rgba(255, 255, 255, 0.04);
}

[data-theme="light"] .course-hub-nav-actions {
  background: rgba(15, 23, 42, 0.03);
}

.course-hub-nav-links {
  display: flex;
  align-items: center;
  gap: 0.35rem;
}

.course-hub-nav-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 40px;
  min-width: 40px;
  padding: 0.4rem 0.85rem;
  border: 1px solid var(--rm-topbar-btn-border);
  border-radius: 10px;
  background: var(--rm-topbar-btn-bg);
  color: var(--rm-topbar-text);
  font-family: var(--course-font);
  font-size: 0.82rem;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s, transform 0.15s;
}

.course-hub-nav-btn:hover {
  background: var(--rm-topbar-btn-hover);
  border-color: var(--rm-accent);
}

.course-theme-toggle--nav {
  min-width: 36px;
  min-height: 36px;
  padding: 0;
  font-size: 1.05rem;
  line-height: 1;
  border: none;
  border-radius: 999px;
  background: transparent;
  color: var(--rm-topbar-text);
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.course-theme-toggle--nav:hover {
  background: var(--rm-topbar-btn-hover);
  color: var(--rm-accent);
}

.course-theme-toggle--hub-nav {
  flex-shrink: 0;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 40px;
  min-height: 40px;
  padding: 0;
  border: 1px solid var(--rm-topbar-btn-border) !important;
  border-radius: 999px;
  background: var(--rm-surface) !important;
  color: #0c2340;
  box-shadow: 0 1px 3px rgba(12, 35, 64, 0.12);
}

[data-theme="dark"] .course-theme-toggle--hub-nav {
  color: #e6edf3;
}

.course-theme-toggle--hub-nav:hover {
  border-color: var(--rm-accent) !important;
  color: var(--rm-accent);
  background: var(--rm-topbar-btn-hover) !important;
}

.course-theme-icon {
  width: 1.15rem;
  height: 1.15rem;
  display: block;
  flex-shrink: 0;
}

.course-hub-nav-actions > .course-theme-toggle--hub-nav + .course-auth-slot--hub-nav {
  padding-left: 0.4rem;
  margin-left: 0.15rem;
  border-left: 1px solid var(--rm-border);
}

.course-auth-slot--hub-nav {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  width: 40px;
  min-width: 40px;
  max-width: 40px;
  overflow: visible;
}

.course-auth-slot--hub-nav:has(.course-auth-user--hub) {
  width: auto;
  min-width: 0;
  max-width: none;
}

.course-auth-slot--hub-nav .course-auth-gbtn--icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  overflow: visible;
  line-height: 0;
}

.course-auth-slot--hub-nav .course-auth-gbtn--icon > div,
.course-auth-slot--hub-nav .course-auth-gbtn--icon iframe {
  display: block !important;
  margin: 0 !important;
}

.course-hub-nav .course-auth-user,
.course-auth-user--hub {
  display: flex;
  align-items: center;
  gap: 0;
  max-width: none;
  padding: 0.15rem 0.15rem 0.15rem 0.3rem;
  border-radius: 999px;
  border: none;
  background: transparent;
  box-shadow: none;
}

.course-hub-nav .course-auth-avatar,
.course-auth-user--hub .course-auth-avatar {
  width: 32px;
  height: 32px;
  border: 2px solid var(--rm-border);
}

.course-hub-nav .course-auth-name,
.course-auth-user--hub .course-auth-name {
  font-size: 0.8rem;
  max-width: 88px;
  padding: 0 0.5rem 0 0.35rem;
}

.course-hub-nav .course-auth-signout,
.course-auth-user--hub .course-auth-signout {
  border: none;
  background: transparent;
  padding: 0.4rem 0.75rem;
  margin: 0;
  border-left: 1px solid var(--rm-border);
  border-radius: 0 999px 999px 0;
  font-size: 0.75rem;
  color: var(--rm-muted);
}

.course-hub-nav .course-auth-signout:hover,
.course-auth-user--hub .course-auth-signout:hover {
  background: var(--rm-topbar-btn-hover);
  color: var(--rm-text);
}

@media (max-width: 640px) {
  .course-hub-nav-inner {
    min-height: 56px;
    padding: 0 1rem;
    gap: 0.75rem;
  }

  .course-hub-nav-mark {
    width: 34px;
    height: 34px;
    font-size: 0.68rem;
  }

  .course-hub-nav-actions {
    gap: 0.25rem;
    padding: 0.25rem;
  }

  .course-hub-nav .course-auth-name,
  .course-auth-user--hub .course-auth-name {
    display: none;
  }

  .course-hub-nav .course-auth-signout,
  .course-auth-user--hub .course-auth-signout {
    padding: 0.35rem 0.55rem;
    font-size: 0.7rem;
  }
}

.course-auth-slot {
  display: flex;
  align-items: center;
  min-height: 40px;
}

/* ── Auth gate (required login) ── */
.course-auth-gate[hidden] {
  display: none !important;
}

.course-auth-gate {
  position: fixed;
  inset: 0;
  z-index: 10000;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1.25rem;
  background: rgba(8, 10, 18, 0.72);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

[data-theme="light"] .course-auth-gate {
  background: rgba(248, 250, 252, 0.82);
}

.course-auth-gate-card {
  width: min(100%, 400px);
  padding: 2rem 1.75rem;
  border-radius: 16px;
  border: 1px solid var(--rm-border);
  background: var(--rm-surface);
  box-shadow: 0 24px 64px rgba(0, 0, 0, 0.35);
  text-align: center;
}

[data-theme="light"] .course-auth-gate-card {
  box-shadow: 0 24px 48px rgba(15, 23, 42, 0.12);
}

.course-auth-gate-badge {
  display: inline-block;
  margin-bottom: 0.85rem;
  padding: 0.3rem 0.75rem;
  border-radius: 999px;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  color: var(--rm-accent);
  background: var(--rm-surface2);
  border: 1px solid var(--rm-border);
}

.course-auth-gate-title {
  margin: 0 0 0.5rem;
  font-family: var(--course-serif);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--rm-text);
  line-height: 1.25;
}

.course-auth-gate-desc {
  margin: 0 0 1.5rem;
  font-size: 0.9rem;
  color: var(--rm-muted);
  line-height: 1.5;
}

.course-auth-gate-btn {
  display: flex;
  justify-content: center;
  min-height: 44px;
}

body.course-auth-locked > *:not(#course-auth-gate):not(script) {
  visibility: hidden;
  pointer-events: none;
}

/* Google Sign-In iframes must stay clickable when gate is open */
body.course-auth-locked iframe[src*="accounts.google.com"],
body.course-auth-gate-open iframe[src*="accounts.google.com"] {
  visibility: visible !important;
  pointer-events: auto !important;
}

body.course-auth-gate-open {
  overflow: hidden;
}

.course-auth-slot--topbar {
  flex-shrink: 0;
}

.course-auth-user {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  max-width: 200px;
}

.course-auth-avatar {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  object-fit: cover;
  border: 1px solid var(--rm-border);
  flex-shrink: 0;
}

.course-auth-name {
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--rm-text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 72px;
}

.course-auth-signout {
  font-family: var(--course-font);
  font-size: 0.72rem;
  font-weight: 600;
  padding: 0.3rem 0.55rem;
  border: 1px solid var(--rm-border);
  border-radius: 6px;
  background: var(--rm-surface2);
  color: var(--rm-muted);
  cursor: pointer;
  white-space: nowrap;
}

.course-auth-signout:hover {
  border-color: var(--rm-accent);
  color: var(--rm-text);
}

.course-auth-gbtn {
  display: flex;
  align-items: center;
  line-height: 0;
}

.course-topbar .course-auth-name {
  display: none;
}

@media (min-width: 901px) {
  .course-topbar .course-auth-name {
    display: inline;
  }
}

.course-hub-hero {
  position: relative;
  overflow: hidden;
  padding: 3rem 1.5rem 2.25rem;
  background: var(--rm-bg);
  color: var(--rm-text);
  text-align: center;
  border-bottom: none;
}

.course-hub-hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 20% 10%, rgba(15, 110, 86, 0.35), transparent),
    radial-gradient(ellipse 60% 50% at 80% 80%, rgba(184, 134, 11, 0.2), transparent);
  pointer-events: none;
}

[data-theme="light"] .course-hub-hero::before {
  background:
    radial-gradient(ellipse 80% 60% at 20% 10%, rgba(15, 110, 86, 0.12), transparent),
    radial-gradient(ellipse 60% 50% at 80% 80%, rgba(184, 134, 11, 0.08), transparent);
}

.course-hub-hero > * {
  position: relative;
  z-index: 1;
}

.course-hub-badge {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.35rem 0.85rem;
  border-radius: 999px;
  margin-bottom: 1.25rem;
}

[data-theme="dark"] .course-hub-badge {
  background: rgba(255, 255, 255, 0.12);
  border: 1px solid rgba(255, 255, 255, 0.2);
}

[data-theme="light"] .course-hub-badge {
  background: rgba(15, 110, 86, 0.1);
  border: 1px solid rgba(15, 110, 86, 0.25);
  color: var(--course-teal);
}

.course-hub-hero h1 {
  font-family: var(--course-serif);
  font-size: clamp(1.85rem, 5vw, 3rem);
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 0.75rem;
}

.course-hub-hero p {
  font-size: clamp(1rem, 2.5vw, 1.15rem);
  opacity: 0.9;
  max-width: 560px;
  margin: 0 auto 1.75rem;
}

.course-hub-cta {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  min-height: 48px;
  padding: 0.75rem 1.75rem;
  border-radius: 999px;
  background: var(--course-teal);
  color: #fff;
  font-weight: 700;
  font-size: 1rem;
  text-decoration: none;
  box-shadow: 0 4px 20px rgba(15, 110, 86, 0.4);
  transition: transform 0.15s, box-shadow 0.15s;
}

.course-hub-cta:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 28px rgba(15, 110, 86, 0.45);
}

.course-hub-cta.secondary {
  box-shadow: none;
  margin-left: 0.75rem;
}

[data-theme="dark"] .course-hub-cta.secondary {
  background: rgba(255, 255, 255, 0.12);
  border: 1px solid rgba(255, 255, 255, 0.3);
  color: #fff;
}

[data-theme="light"] .course-hub-cta.secondary {
  background: var(--rm-surface);
  border: 1px solid var(--rm-border);
  color: var(--rm-text);
}

.course-hub-cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  justify-content: center;
}

.course-hub-main {
  max-width: 920px;
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
}

.course-hub-progress {
  text-align: center;
  font-size: 0.9rem;
  color: var(--rm-muted);
  margin-bottom: 1.5rem;
}

.course-hub-progress strong {
  color: var(--rm-done);
}

.course-hub-section-title {
  font-family: var(--course-serif);
  font-size: 1.35rem;
  color: var(--rm-text);
  margin-bottom: 0.35rem;
  text-align: center;
}

.course-hub-section-sub {
  font-size: 0.92rem;
  color: var(--rm-muted);
  margin-bottom: 2rem;
  text-align: center;
}

/* ── Roadmap canvas ── */
.roadmap-canvas {
  position: relative;
  max-width: 640px;
  margin: 0 auto;
}

.roadmap-track-label {
  display: inline-block;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--rm-muted);
  background: var(--rm-surface2);
  border: 1px solid var(--rm-border);
  padding: 0.25rem 0.65rem;
  border-radius: 999px;
  margin-bottom: 1rem;
}

.roadmap-spine {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0;
}

.roadmap-step {
  display: flex;
  flex-direction: column;
  align-items: center;
  width: 100%;
}

.roadmap-connector {
  width: 2px;
  height: 28px;
  background: var(--rm-border);
  flex-shrink: 0;
}

.roadmap-connector.fork-split {
  height: 20px;
  position: relative;
}

.roadmap-fork-wrap {
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.roadmap-fork-row {
  display: flex;
  gap: 1rem;
  width: 100%;
  justify-content: center;
  position: relative;
}

.roadmap-fork-row::before {
  content: '';
  position: absolute;
  top: 0;
  left: 25%;
  right: 25%;
  height: 2px;
  background: var(--rm-border);
}

.roadmap-fork-col {
  flex: 1;
  max-width: 280px;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.roadmap-fork-col .roadmap-connector {
  height: 20px;
}

.roadmap-node {
  display: block;
  width: 100%;
  max-width: 320px;
  padding: 1rem 1.15rem;
  background: var(--rm-surface);
  border: 2px solid var(--rm-border);
  border-radius: 12px;
  text-decoration: none;
  color: var(--rm-text);
  transition: border-color 0.15s, box-shadow 0.15s, transform 0.15s;
  text-align: left;
}

.roadmap-node:hover {
  transform: translateY(-2px);
  border-color: var(--rm-accent);
  box-shadow: var(--rm-node-shadow);
}

.roadmap-node.done {
  border-color: var(--rm-done);
}

.roadmap-node.done .roadmap-node-status::after {
  content: ' ✓';
  color: var(--rm-done);
}

.roadmap-node.current {
  border-color: var(--rm-accent);
  box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.25);
}

.roadmap-node.next {
  opacity: 0.85;
}

.roadmap-node-head {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  margin-bottom: 0.4rem;
}

.roadmap-node-num {
  width: 32px;
  height: 32px;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.8rem;
  font-weight: 700;
  flex-shrink: 0;
  background: var(--rm-surface2);
  border: 1px solid var(--rm-border);
}

.roadmap-node.color-teal .roadmap-node-num { border-color: var(--rm-node-teal); color: var(--rm-node-teal); }
.roadmap-node.color-blue .roadmap-node-num { border-color: var(--rm-node-blue); color: var(--rm-node-blue); }
.roadmap-node.color-amber .roadmap-node-num { border-color: var(--rm-node-amber); color: var(--rm-node-amber); }
.roadmap-node.color-purple .roadmap-node-num { border-color: var(--rm-node-purple); color: var(--rm-node-purple); }
.roadmap-node.color-rose .roadmap-node-num { border-color: var(--rm-node-rose); color: var(--rm-node-rose); }
.roadmap-node.color-green .roadmap-node-num { border-color: var(--rm-node-green); color: var(--rm-node-green); }

.roadmap-node.color-teal.done { border-color: var(--rm-node-teal); }
.roadmap-node.color-blue.done { border-color: var(--rm-node-blue); }
.roadmap-node.color-amber.done { border-color: var(--rm-node-amber); }
.roadmap-node.color-purple.done { border-color: var(--rm-node-purple); }
.roadmap-node.color-rose.done { border-color: var(--rm-node-rose); }
.roadmap-node.color-green.done { border-color: var(--rm-node-green); }

.roadmap-node-title {
  font-size: 1rem;
  font-weight: 700;
  line-height: 1.25;
}

.roadmap-node-status {
  font-size: 0.68rem;
  color: var(--rm-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.roadmap-node p {
  font-size: 0.85rem;
  color: var(--rm-muted);
  margin: 0 0 0.5rem;
  line-height: 1.5;
}

.roadmap-node-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}

.roadmap-chip {
  font-size: 0.68rem;
  font-weight: 600;
  padding: 0.15rem 0.5rem;
  border-radius: 999px;
  background: var(--rm-surface2);
  border: 1px solid var(--rm-border);
  color: var(--rm-muted);
}

.roadmap-chip.duration {
  color: var(--rm-node-amber);
  border-color: rgba(210, 153, 34, 0.4);
}

.roadmap-node-title-row {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  min-width: 0;
}

.roadmap-node-title-row .roadmap-node-title {
  flex: 1;
  min-width: 0;
}

.lecture-hero-title-row {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.65rem;
  margin-bottom: 0.5em;
}

.lecture-hero-title-row h1 {
  margin-bottom: 0;
}

.lecture-video-trigger {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  padding: 0;
  flex-shrink: 0;
  border: 1.5px solid var(--rm-accent, #0f6e56);
  border-radius: 50%;
  background: var(--rm-surface2, rgba(255, 255, 255, 0.08));
  color: var(--rm-accent, #0f6e56);
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s, transform 0.15s, box-shadow 0.15s;
}

.lecture-video-trigger:hover {
  background: var(--rm-surface, #fff);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(15, 110, 86, 0.18);
}

.lecture-video-trigger:focus-visible {
  outline: 2px solid var(--rm-accent, #0f6e56);
  outline-offset: 2px;
}

.lecture-video-icon {
  width: 18px;
  height: 18px;
}

.roadmap-node .lecture-video-trigger {
  width: 30px;
  height: 30px;
}

.roadmap-node .lecture-video-icon {
  width: 16px;
  height: 16px;
}

.lecture-video-overlay {
  position: fixed;
  inset: 0;
  z-index: 10050;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  background: rgba(8, 10, 18, 0.78);
  backdrop-filter: blur(6px);
  -webkit-backdrop-filter: blur(6px);
}

.lecture-video-overlay.is-open {
  display: flex;
}

.lecture-video-dialog {
  position: relative;
  width: min(920px, 100%);
  background: var(--rm-surface, #161b22);
  border: 1px solid var(--rm-border, #30363d);
  border-radius: 14px;
  padding: 0.75rem;
  box-shadow: 0 24px 60px rgba(0, 0, 0, 0.45);
}

.lecture-video-close {
  position: absolute;
  top: -0.35rem;
  right: -0.35rem;
  z-index: 2;
  width: 36px;
  height: 36px;
  border: 1px solid var(--rm-border, #30363d);
  border-radius: 50%;
  background: var(--rm-surface, #161b22);
  color: var(--rm-text, #e6edf3);
  font-size: 1.4rem;
  line-height: 1;
  cursor: pointer;
}

.lecture-video-close:hover {
  border-color: var(--rm-accent, #0f6e56);
  color: var(--rm-accent, #0f6e56);
}

.lecture-video-frame-wrap {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  border-radius: 10px;
  overflow: hidden;
  background: #000;
}

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

body.lecture-video-open {
  overflow: hidden;
}

[data-theme="light"] .lecture-video-overlay {
  background: rgba(248, 250, 252, 0.88);
}

[data-theme="light"] .lecture-video-dialog {
  background: #fff;
}

.course-hub-footer {
  text-align: center;
  padding: 2rem 1rem;
  font-size: 0.85rem;
  color: var(--rm-muted);
  border-top: 1px solid var(--rm-border);
}

@media (max-width: 600px) {
  .roadmap-fork-row {
    flex-direction: column;
    align-items: center;
    gap: 0;
  }

  .roadmap-fork-row::before {
    display: none;
  }

  .roadmap-fork-col {
    max-width: 320px;
    width: 100%;
  }
}

@media (min-width: 601px) {
  .roadmap-fork-row:has(.roadmap-fork-col:nth-child(3))::before {
    left: 15%;
    right: 15%;
  }
}

/* ── Lecture pages: dark shell (dark theme only) ── */
[data-theme="dark"] body.course-page {
  background: var(--rm-bg) !important;
  color: var(--rm-text);
}

[data-theme="dark"] body.course-page .section,
[data-theme="dark"] body.course-page .toc-card,
[data-theme="dark"] body.course-page .pipeline-lab {
  background: var(--rm-surface) !important;
  color: var(--rm-text) !important;
  border-color: var(--rm-border) !important;
}

[data-theme="dark"] body.course-page .page,
[data-theme="dark"] body.course-page .wrapper,
[data-theme="dark"] body.course-page .content,
[data-theme="dark"] body.course-page .toc-wrapper,
[data-theme="dark"] body.course-page .part,
[data-theme="dark"] body.course-page .lr-toc,
[data-theme="dark"] body.course-page #main {
  background: transparent !important;
}

[data-theme="dark"] body.course-page .page-header:not(.yc-lecture-hero) {
  background: var(--rm-surface) !important;
  color: var(--rm-text) !important;
  border-color: var(--rm-border) !important;
}

[data-theme="dark"] body.course-page .page-header h1,
[data-theme="dark"] body.course-page .section-title {
  color: var(--rm-text) !important;
}

[data-theme="dark"] body.course-page .page-header .subtitle,
[data-theme="dark"] body.course-page .section-subtitle,
[data-theme="dark"] body.course-page p,
[data-theme="dark"] body.course-page li {
  color: #c9d1d9;
}

[data-theme="dark"] body.course-page .toc-card,
[data-theme="dark"] body.course-page .pipeline-math-box,
[data-theme="dark"] body.course-page .pipeline-stat,
[data-theme="dark"] body.course-page .box,
[data-theme="dark"] body.course-page .quiz-card,
[data-theme="dark"] body.course-page .learn-card {
  background: var(--rm-surface2) !important;
  border-color: var(--rm-border) !important;
}

[data-theme="dark"] body.course-page #main {
  background: transparent;
}

[data-theme="light"] body.course-page {
  background: transparent;
}

/* ── Theme toggle ── */
.course-theme-toggle {
  font-size: 1.1rem;
  line-height: 1;
  padding: 0.4rem 0.55rem;
}

.course-theme-toggle--hub {
  position: absolute;
  top: max(1rem, env(safe-area-inset-top, 0px));
  right: max(1rem, env(safe-area-inset-right, 0px));
  z-index: 2;
  min-width: 44px;
  min-height: 44px;
  border: 1px solid var(--rm-topbar-btn-border);
  border-radius: 8px;
  background: var(--rm-topbar-btn-bg);
  color: var(--rm-topbar-text);
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
}

.course-theme-toggle--hub:hover {
  background: var(--rm-topbar-btn-hover);
  border-color: var(--rm-accent);
}

.course-timeline {
  list-style: none;
  padding: 0;
  margin: 0;
  position: relative;
}

.course-timeline::before {
  content: '';
  position: absolute;
  left: 23px;
  top: 24px;
  bottom: 24px;
  width: 2px;
  background: linear-gradient(180deg, var(--course-teal), var(--course-gold));
  border-radius: 2px;
}

.course-timeline-item {
  position: relative;
  padding-left: 64px;
  padding-bottom: 1.75rem;
}

.course-timeline-item:last-child {
  padding-bottom: 0;
}

.course-timeline-num {
  position: absolute;
  left: 0;
  top: 0;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--course-white);
  border: 2px solid var(--course-teal);
  color: var(--course-teal);
  font-weight: 700;
  font-size: 0.95rem;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--course-shadow);
  z-index: 1;
}

.course-timeline-card {
  display: block;
  background: var(--course-white);
  border: 1px solid var(--course-border);
  border-radius: var(--course-radius);
  padding: 1.25rem 1.35rem;
  text-decoration: none;
  color: inherit;
  box-shadow: var(--course-shadow);
  transition: transform 0.15s, box-shadow 0.15s, border-color 0.15s;
}

.course-timeline-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--course-shadow-lg);
  border-color: var(--course-teal);
}

.course-timeline-card h3 {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--course-navy);
  margin-bottom: 0.35rem;
}

.course-timeline-card p {
  font-size: 0.92rem;
  color: var(--course-text2);
  margin-bottom: 0.65rem;
}

.course-timeline-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.course-chip {
  font-size: 0.72rem;
  font-weight: 600;
  padding: 0.2rem 0.55rem;
  border-radius: 999px;
  background: var(--course-teal-lt);
  color: var(--course-teal);
}

.course-chip.gold {
  background: var(--course-gold-lt);
  color: var(--course-gold);
}

.course-hub-footer {
  text-align: center;
  padding: 2rem 1rem;
  font-size: 0.85rem;
  color: var(--course-text3);
  border-top: 1px solid var(--course-border);
}

.course-continue-banner {
  display: none;
  margin-top: 1rem;
}

.course-continue-banner.is-visible {
  display: inline-flex;
}

/* ── Global responsive helpers for lecture content ── */
body.course-page table {
  max-width: 100%;
}

body.course-page .math-table-wrap,
body.course-page .glossary-body,
body.course-page .pipeline-math-box .math-table-wrap {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

body.course-page canvas {
  max-width: 100%;
  height: auto;
}

body.course-page .viz-canvas-wrap canvas {
  height: 100% !important;
  max-height: 100%;
}

body.course-page .pipeline-canvas-wrap canvas,
body.course-page .pipeline-canvas-wrap {
  max-width: 100%;
}

@media (max-width: 520px) {
  .course-footer-nav--yc .course-footer-btn .footer-label {
    display: none;
  }

  .course-footer-nav--yc .course-footer-btn {
    min-width: 44px;
    padding: 0.5rem;
  }

  .course-footer-nav--yc .course-footer-btn--hub .footer-label {
    display: inline;
  }
}

@media (max-width: 900px) {
  .course-topbar-menu.course-drawer-toggle {
    display: inline-flex;
  }

  .course-topbar-nav .nav-text {
    display: none;
  }

  .course-topbar-nav-btn {
    min-width: 36px;
    padding: 0.35rem 0.55rem;
  }

  .course-topbar-module {
    border-left: none;
    padding-left: 0;
    margin-left: 0;
  }

  .course-topbar--yc .course-topbar-title {
    font-size: 0.82rem;
  }
}

@media (max-width: 768px) {
  .course-topbar-btn span.btn-label {
    display: none;
  }

  .course-topbar-title {
    font-size: 0.8rem;
  }

  .course-hub-cta.secondary {
    margin-left: 0;
  }

  body.course-page .toc-grid,
  body.course-page .industry-grid,
  body.course-page .k-compare-grid,
  body.course-page .grid-2,
  body.course-page .grid-3,
  body.course-page .analogy-box {
    grid-template-columns: 1fr !important;
  }

  body.course-page .page-header h1 {
    font-size: clamp(1.5rem, 6vw, 2rem) !important;
  }

  body.course-page .header-meta {
    flex-wrap: wrap !important;
    gap: 0.5rem !important;
  }

  body.course-page .pipeline-live-ctrl {
    flex-direction: column !important;
    align-items: stretch !important;
  }

  body.course-page .pipeline-live-ctrl input[type=range] {
    width: 100% !important;
  }
}

@media (max-width: 480px) {
  .course-timeline::before {
    left: 19px;
  }

  .course-timeline-item {
    padding-left: 56px;
  }

  .course-timeline-num {
    width: 40px;
    height: 40px;
    font-size: 0.85rem;
  }

  .course-footer-btn {
    font-size: 0.78rem;
    padding: 0.45rem 0.5rem;
  }
}

@media (min-width: 901px) {
  body.course-page .course-footer-nav {
    display: none;
  }

  body.course-page {
    padding-bottom: 0;
  }
}

@media print {
  .course-topbar,
  .course-progress-wrap,
  .course-footer-nav,
  .course-drawer-toggle,
  .course-drawer-overlay {
    display: none !important;
  }

  body.course-page {
    padding-top: 0;
    padding-bottom: 0;
  }
}

/* ── YC startup hub (index only) — layout YC, palette original teal/cream ── */
.course-hub--yc {
  --yc-font: 'Inter', 'Hind Siliguri', system-ui, sans-serif;
  background: var(--rm-bg);
  color: var(--rm-text);
  font-family: var(--yc-font);
}

.course-hub--yc .course-hub-nav {
  background: rgba(250, 248, 244, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--rm-border);
  box-shadow: none;
}

[data-theme="dark"] .course-hub--yc .course-hub-nav {
  background: rgba(13, 17, 23, 0.88);
  border-bottom-color: var(--rm-border);
}

.course-hub--yc .course-hub-nav-mark {
  background: linear-gradient(145deg, var(--course-teal), #0d5c47);
  box-shadow: 0 2px 10px rgba(15, 110, 86, 0.35);
  border-radius: 8px;
}

.course-hub--yc .course-hub-nav-actions {
  border-color: var(--rm-border);
  background: var(--rm-topbar-btn-bg);
}

.course-hub--yc .course-hub-hero {
  text-align: left;
  padding: 4.5rem 1.5rem 3.5rem;
  background: var(--rm-bg);
  border-bottom: 1px solid var(--rm-border);
  position: relative;
  overflow: hidden;
}

.course-hub--yc .course-hub-hero::before {
  display: block;
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 20% 10%, rgba(15, 110, 86, 0.28), transparent),
    radial-gradient(ellipse 60% 50% at 80% 80%, rgba(184, 134, 11, 0.18), transparent);
  pointer-events: none;
}

[data-theme="light"] .course-hub--yc .course-hub-hero::before {
  background:
    radial-gradient(ellipse 80% 60% at 20% 10%, rgba(15, 110, 86, 0.14), transparent),
    radial-gradient(ellipse 60% 50% at 80% 80%, rgba(184, 134, 11, 0.1), transparent);
}

.course-hub--yc .yc-hero-inner {
  position: relative;
  z-index: 1;
  max-width: 1100px;
  margin: 0 auto;
}

.course-hub--yc .yc-eyebrow {
  margin: 0 0 1.25rem;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--course-teal);
}

.course-hub--yc .course-hub-hero h1 {
  font-family: var(--yc-font);
  font-size: clamp(2.25rem, 6vw, 3.75rem);
  font-weight: 800;
  line-height: 1.08;
  letter-spacing: -0.03em;
  color: var(--rm-text);
  margin: 0 0 1.25rem;
  max-width: 16ch;
}

.course-hub--yc .yc-hero-accent {
  color: var(--course-teal);
}

.course-hub--yc .yc-lead {
  font-size: clamp(1.05rem, 2.2vw, 1.25rem);
  line-height: 1.6;
  color: var(--rm-muted);
  max-width: 52ch;
  margin: 0 0 2rem;
  opacity: 1;
}

.course-hub--yc .yc-cta-row {
  justify-content: flex-start;
  gap: 0.85rem;
  margin-bottom: 3rem;
}

.course-hub--yc .yc-cta-primary {
  border-radius: 999px;
  background: var(--course-teal);
  color: #fff;
  font-family: var(--yc-font);
  font-weight: 700;
  font-size: 0.95rem;
  padding: 0.85rem 1.5rem;
  min-height: 48px;
  border: 1px solid var(--course-teal);
  box-shadow: 0 4px 20px rgba(15, 110, 86, 0.4);
}

.course-hub--yc .yc-cta-primary:hover {
  background: #0b6049;
  border-color: #0b6049;
  transform: translateY(-2px);
  box-shadow: 0 8px 28px rgba(15, 110, 86, 0.45);
}

.course-hub--yc .yc-cta-secondary {
  border-radius: 999px;
  margin-left: 0;
  font-family: var(--yc-font);
  font-weight: 600;
  font-size: 0.95rem;
  padding: 0.85rem 1.5rem;
  background: var(--rm-surface);
  border: 1px solid var(--rm-border);
  color: var(--rm-text);
  box-shadow: none;
}

.course-hub--yc .yc-cta-secondary:hover {
  border-color: var(--course-teal);
  background: var(--rm-surface2);
  transform: translateY(-1px);
}

.course-hub--yc .yc-stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  margin: 0;
  padding: 0;
  max-width: 520px;
  border: 1px solid var(--rm-border);
  border-radius: 12px;
  overflow: hidden;
  background: var(--rm-border);
}

.course-hub--yc .yc-stat {
  margin: 0;
  padding: 1rem 1.1rem;
  background: var(--rm-surface);
}

.course-hub--yc .yc-stat dt {
  margin: 0 0 0.35rem;
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--rm-muted);
}

.course-hub--yc .yc-stat dd {
  margin: 0;
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--rm-text);
}

.course-hub--yc .yc-main {
  max-width: 920px;
  margin: 0 auto;
  padding: 3.5rem 1.5rem 5rem;
  background: var(--rm-bg);
  display: flex;
  flex-direction: column;
  align-items: center;
}

.course-hub--yc .yc-section-head {
  width: 100%;
  max-width: 640px;
  margin-bottom: 2.5rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--rm-border);
  text-align: center;
}

.course-hub--yc .yc-section-label {
  margin: 0 0 0.5rem;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--course-teal);
}

.course-hub--yc .course-hub-section-title {
  font-family: var(--course-serif);
  font-size: clamp(1.5rem, 3vw, 2rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  text-align: center;
  margin: 0 0 0.5rem;
  color: var(--rm-text);
}

.course-hub--yc .course-hub-progress {
  text-align: center;
  margin: 0 auto;
  font-size: 0.92rem;
  color: var(--rm-muted);
}

.course-hub--yc .course-hub-progress strong {
  color: var(--rm-done);
}

.course-hub--yc .roadmap-canvas {
  width: 100%;
  max-width: 640px;
  margin: 0 auto;
}

.course-hub--yc .roadmap-track {
  display: flex;
  flex-direction: column;
  align-items: center;
  width: 100%;
}

.course-hub--yc .roadmap-track-label {
  font-family: var(--yc-font);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  color: var(--rm-muted);
  background: var(--rm-surface2);
  border-color: var(--rm-border);
  border-radius: 999px;
}

.course-hub--yc .roadmap-node {
  border-radius: var(--course-radius);
  box-shadow: var(--rm-node-shadow);
  transition: transform 0.15s, box-shadow 0.15s;
}

.course-hub--yc .roadmap-node:hover {
  transform: translateY(-2px);
  box-shadow: var(--course-shadow-lg);
}

.course-hub--yc .roadmap-node.current {
  border-color: var(--rm-accent);
  box-shadow: 0 0 0 3px rgba(15, 110, 86, 0.2);
}

[data-theme="dark"] .course-hub--yc .roadmap-node.current {
  box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.2);
}

.course-hub--yc .roadmap-node-title {
  font-family: var(--course-font);
  font-weight: 600;
}

.course-hub--yc .yc-footer {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 1.75rem 1.5rem;
  font-family: var(--yc-font);
  font-size: 0.8rem;
  color: var(--rm-muted);
  border-top: 1px solid var(--rm-border);
  background: var(--rm-bg);
}

.course-hub--yc .yc-footer-dot {
  opacity: 0.4;
}

.course-hub--yc .course-continue-banner.is-visible {
  display: inline-flex;
}

@media (max-width: 720px) {
  .course-hub--yc .course-hub-hero {
    padding: 3rem 1.25rem 2.5rem;
  }

  .course-hub--yc .yc-stats {
    grid-template-columns: repeat(2, 1fr);
    max-width: 100%;
  }

  .course-hub--yc .yc-cta-row {
    flex-direction: column;
    align-items: stretch;
  }

  .course-hub--yc .yc-cta-primary,
  .course-hub--yc .yc-cta-secondary {
    justify-content: center;
    width: 100%;
  }
}

/* ── YC lecture skin (ML Data Processing) — layout YC, palette teal/cream ── */
body.course-page--yc {
  --yc-font: 'Inter', 'Hind Siliguri', system-ui, sans-serif;
  font-family: var(--yc-font);
  background: var(--rm-bg);
  color: var(--rm-text);
}

body.course-page--yc #sidebar {
  top: calc(var(--course-topbar-h) + env(safe-area-inset-top, 0px));
  height: calc(100vh - var(--course-topbar-h) - env(safe-area-inset-top, 0px));
  background: var(--rm-surface);
  color: var(--rm-muted);
  border-right: 1px solid var(--rm-border);
  box-shadow: none;
}

body.course-page--yc #sidebar::-webkit-scrollbar-thumb {
  background: var(--rm-border);
}

body.course-page--yc .sidebar-header {
  border-bottom-color: var(--rm-border);
  padding-top: 1.25rem;
}

body.course-page--yc .sidebar-badge {
  font-family: var(--yc-font);
  font-size: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--course-teal);
  background: var(--course-teal-lt);
  border-radius: 999px;
  padding: 0.3rem 0.65rem;
}

body.course-page--yc .sidebar-title {
  font-family: var(--yc-font);
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--rm-text);
  letter-spacing: -0.02em;
}

body.course-page--yc .sidebar-sub {
  font-family: var(--yc-font);
  font-size: 0.72rem;
  color: var(--rm-muted);
}

body.course-page--yc .nav-section {
  font-family: var(--yc-font);
  color: var(--rm-muted);
  opacity: 0.85;
}

body.course-page--yc .nav-item {
  font-family: var(--yc-font);
  font-size: 0.82rem;
  color: var(--rm-muted);
  border-left-color: transparent;
  border-radius: 0 8px 8px 0;
  margin-right: 0.5rem;
}

body.course-page--yc .nav-item:hover {
  color: var(--rm-text);
  background: var(--rm-surface2);
  border-left-color: var(--course-teal);
}

body.course-page--yc .nav-item.active {
  color: var(--course-teal);
  background: var(--course-teal-lt);
  border-left-color: var(--course-teal);
  font-weight: 600;
}

body.course-page--yc .nav-num {
  font-family: var(--course-mono);
  color: var(--rm-muted);
}

body.course-page--yc .nav-item.active .nav-num {
  color: var(--course-teal);
}

body.course-page--yc .progress-wrap {
  border-top-color: var(--rm-border);
}

body.course-page--yc .progress-label {
  font-family: var(--yc-font);
  color: var(--rm-muted);
}

body.course-page--yc .progress-bar {
  background: var(--rm-progress-track);
  height: 4px;
  border-radius: 999px;
}

body.course-page--yc .progress-fill {
  background: linear-gradient(90deg, var(--course-teal), #22c55e);
  border-radius: 999px;
}

body.course-page--yc #main {
  background: var(--rm-bg);
}

body.course-page--yc .yc-lecture-hero-inner > * {
  animation: ycFadeUp .5s ease both;
}

body.course-page--yc .yc-lecture-eyebrow { animation-delay: .1s; }
body.course-page--yc .yc-lecture-hero h1 { animation-delay: .2s; }
body.course-page--yc .yc-lecture-lead { animation-delay: .3s; }
body.course-page--yc .yc-lecture-stats { animation-delay: .4s; }
body.course-page--yc .yc-lecture-chips { animation-delay: .5s; }

@keyframes ycFadeUp {
  from { opacity: 0; transform: translateY(16px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Cream/YC hero chrome — NOT for .page-header (Brand Kit owns that gradient) */
body.course-page--yc .yc-lecture-hero:not(.page-header) {
  background: var(--rm-bg);
  color: var(--rm-text);
  padding: 3.5rem 2.5rem 3rem;
  border-bottom: 1px solid var(--rm-border);
}

body.course-page--yc .yc-lecture-hero:not(.page-header)::before {
  background:
    radial-gradient(ellipse 80% 60% at 20% 10%, rgba(15, 110, 86, 0.2), transparent),
    radial-gradient(ellipse 60% 50% at 80% 80%, rgba(184, 134, 11, 0.12), transparent);
}

[data-theme="light"] body.course-page--yc .yc-lecture-hero:not(.page-header)::before {
  background:
    radial-gradient(ellipse 80% 60% at 20% 10%, rgba(15, 110, 86, 0.12), transparent),
    radial-gradient(ellipse 60% 50% at 80% 80%, rgba(184, 134, 11, 0.08), transparent);
}

body.course-page--yc .yc-lecture-hero:not(.page-header)::after {
  display: none;
}

body.course-page--yc .yc-lecture-hero-inner {
  position: relative;
  z-index: 1;
  max-width: 900px;
}

body.course-page--yc .yc-lecture-eyebrow {
  font-family: var(--yc-font);
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--course-teal);
  margin: 0 0 1rem;
}

body.course-page--yc .yc-lecture-eyebrow::before {
  display: none;
}

body.course-page--yc .yc-lecture-hero:not(.page-header) h1 {
  font-family: var(--yc-font);
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 800;
  line-height: 1.08;
  letter-spacing: -0.03em;
  color: var(--rm-text);
  max-width: 18ch;
}

body.course-page--yc .yc-lecture-hero:not(.page-header) h1 span {
  color: var(--course-teal);
}

body.course-page--yc .yc-lecture-lead {
  font-size: clamp(1rem, 2vw, 1.15rem);
  line-height: 1.6;
  color: var(--rm-muted);
  max-width: 52ch;
  margin: 1.25rem 0 2rem;
}

body.course-page--yc .yc-lecture-stats {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 1rem;
  max-width: 520px;
  margin: 0 0 2rem;
}

body.course-page--yc .yc-lecture-stat {
  padding: 0.85rem 1rem;
  background: var(--rm-surface);
  border: 1px solid var(--rm-border);
  border-radius: 12px;
}

body.course-page--yc .yc-lecture-stat dt {
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--rm-muted);
  margin-bottom: 0.25rem;
}

body.course-page--yc .yc-lecture-stat dd {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--rm-text);
  margin: 0;
}

body.course-page--yc .yc-lecture-chips {
  margin-top: 0;
}

body.course-page--yc .chip {
  font-family: var(--yc-font);
  font-size: 0.72rem;
  font-weight: 600;
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
  letter-spacing: 0.02em;
}

body.course-page--yc .chip-teal {
  background: var(--course-teal-lt);
  color: var(--course-teal);
  border-color: rgba(15, 110, 86, 0.2);
}

body.course-page--yc .chip-amber {
  background: var(--course-gold-lt);
  color: #9a6700;
  border-color: rgba(184, 134, 11, 0.25);
}

body.course-page--yc .chip-violet {
  background: #ede7f6;
  color: #6e40c9;
  border-color: rgba(110, 64, 201, 0.2);
}

body.course-page--yc .chip-cobalt {
  background: #e5eafe;
  color: #185fa5;
  border-color: rgba(24, 95, 165, 0.2);
}

body.course-page--yc .content,
body.course-page--yc .toc-wrapper,
body.course-page--yc .lr-toc {
  max-width: 900px;
  margin-left: auto;
  margin-right: auto;
  padding-left: clamp(1rem, 3vw, 2.5rem);
  padding-right: clamp(1rem, 3vw, 2.5rem);
}

body.course-page--yc .content {
  padding-bottom: 5rem;
}

body.course-page--yc .toc-wrapper {
  padding-top: 0;
  padding-bottom: 0;
}

/* ── Unified lecture surface (ML Features reference — all layouts) ── */
body.course-page--yc .content,
body.course-page--yc #main .content {
  font-size: 15px;
  line-height: 1.75;
}

body.course-page--yc .part,
body.course-page--yc .toc-card,
body.course-page--yc .lr-toc,
body.course-page--yc #main .section-block,
body.course-page--yc #main .hero + .content > .section {
  background: var(--rm-surface);
  border: 1px solid var(--rm-border);
  border-radius: var(--course-radius-sm);
  padding: 1.75rem;
  margin-bottom: 1rem;
  box-shadow: none;
}

body.course-page--yc .toc-wrapper .toc-card {
  margin-top: 1rem;
}

body.course-page--yc .part-header {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  border-bottom: 1px solid var(--rm-border);
  margin-bottom: 1.25rem;
  padding-bottom: 1rem;
}

body.course-page--yc .part-num,
body.course-page--yc .part-num.blue,
body.course-page--yc .part-num.teal,
body.course-page--yc .part-num.amber,
body.course-page--yc .part-num.purple,
body.course-page--yc .part-num.coral,
body.course-page--yc .part-num.green,
body.course-page--yc .part-num.red,
body.course-page--yc .part-num.pink,
body.course-page--yc .part-num.gray {
  width: 36px;
  height: 36px;
  min-width: 36px;
  font-size: 13px;
  font-weight: 700;
  color: var(--course-teal) !important;
  background: var(--course-teal-lt) !important;
  border-radius: 999px;
}

body.course-page--yc .part h3,
body.course-page--yc .content h3,
body.course-page--yc #main h3 {
  font-family: var(--yc-font);
  font-size: 1rem;
  font-weight: 700;
  margin: 1.35rem 0 0.65rem;
  color: var(--rm-text);
}

body.course-page--yc .part h4,
body.course-page--yc .content h4,
body.course-page--yc #main h4 {
  font-family: var(--yc-font);
  font-size: 0.9rem;
  font-weight: 600;
  margin: 1rem 0 0.45rem;
  color: var(--rm-muted);
}

body.course-page--yc .card-colored,
body.course-page--yc .story-box,
body.course-page--yc .explain-box,
body.course-page--yc .card-teal,
body.course-page--yc .card-blue,
body.course-page--yc .card-amber,
body.course-page--yc .card-coral,
body.course-page--yc .card-purple,
body.course-page--yc .card-green,
body.course-page--yc .card-pink,
body.course-page--yc .cc,
body.course-page--yc .cb,
body.course-page--yc .ct,
body.course-page--yc .ca,
body.course-page--yc .co,
body.course-page--yc .cp,
body.course-page--yc .cg,
body.course-page--yc .cr,
body.course-page--yc .ck {
  background: var(--rm-surface2) !important;
  border-left: 3px solid var(--course-teal) !important;
  border-radius: 0 var(--course-radius-sm) var(--course-radius-sm) 0 !important;
  box-shadow: none !important;
  color: var(--rm-text);
}

body.course-page--yc .mistake-box,
body.course-page--yc .mb {
  background: #fdf6f6 !important;
  border-left: 3px solid #c45c5c !important;
  border-radius: 0 var(--course-radius-sm) var(--course-radius-sm) 0 !important;
  box-shadow: none !important;
}

body.course-page--yc .card-colored strong,
body.course-page--yc .story-box h3,
body.course-page--yc .explain-box,
body.course-page--yc .highlight-box strong {
  color: var(--course-teal);
}

body.course-page--yc .card,
body.course-page--yc .formula-box,
body.course-page--yc .visual-container,
body.course-page--yc .vc,
body.course-page--yc .bayes-lab,
body.course-page--yc #main .box,
body.course-page--yc #main .info-box {
  background: var(--rm-surface2);
  border: 1px solid var(--rm-border);
  border-radius: var(--course-radius-sm);
  box-shadow: none;
}

body.course-page--yc .part p,
body.course-page--yc .content p,
body.course-page--yc #main p {
  color: var(--rm-text);
  margin-bottom: 0.75rem;
}

body.course-page--yc .part-title-wrap .time-badge,
body.course-page--yc .toc-grid .num {
  color: var(--rm-muted);
  font-size: 12px;
}

body.course-page--yc thead th,
body.course-page--yc #main thead th {
  background: var(--course-teal) !important;
  color: #fff !important;
  border: none;
}

body.course-page--yc .badge-yes,
body.course-page--yc .by {
  background: var(--course-teal-lt) !important;
  color: var(--course-teal) !important;
}

body.course-page--yc .badge-no,
body.course-page--yc .bn {
  background: #fcebeb !important;
  color: #a32d2d !important;
}

body.course-page--yc .section-header {
  border-bottom: 1px solid var(--rm-border);
  gap: 1rem;
  margin-bottom: 1.75rem;
  padding-bottom: 1rem;
}

body.course-page--yc .section-num {
  font-family: var(--yc-font);
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--course-teal);
  background: var(--course-teal-lt);
  border-radius: 999px;
  padding: 0.35rem 0.75rem;
}

body.course-page--yc .section h2 {
  font-family: var(--yc-font);
  font-size: clamp(1.5rem, 3vw, 2rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--rm-text);
}

body.course-page--yc .subsection h3 {
  font-family: var(--yc-font);
  font-size: 1.2rem;
  font-weight: 700;
  letter-spacing: -0.01em;
}

body.course-page--yc .subsection h3::before {
  background: var(--course-teal);
  border-radius: 999px;
}

body.course-page--yc p {
  color: var(--rm-text);
  line-height: 1.7;
}

body.course-page--yc .callout {
  border-radius: var(--course-radius-sm);
  border-left-width: 3px;
  box-shadow: var(--course-shadow);
}

body.course-page--yc .callout strong {
  font-family: var(--yc-font);
  font-weight: 700;
  letter-spacing: 0.04em;
}

body.course-page--yc .pipeline-step {
  background: var(--rm-surface);
  color: var(--rm-text);
  border: 1px solid var(--rm-border);
  border-radius: 10px;
  font-family: var(--yc-font);
  box-shadow: var(--course-shadow);
}

body.course-page--yc .pipeline-step .step-label {
  font-family: var(--course-mono);
  color: var(--rm-muted);
}

body.course-page--yc .pipeline-step.highlight {
  background: var(--course-teal);
  color: #fff;
  border-color: var(--course-teal);
}

body.course-page--yc .pipeline-step.highlight .step-label {
  color: rgba(255, 255, 255, 0.75);
}

body.course-page--yc .pipeline-step.final {
  background: #0b6049;
  border-color: #0b6049;
  color: #fff;
}

body.course-page--yc .tbl-wrap {
  border-radius: var(--course-radius-sm);
  border-color: var(--rm-border);
  box-shadow: var(--course-shadow);
  overflow: hidden;
}

body.course-page--yc thead tr {
  background: var(--course-teal);
}

body.course-page--yc thead th {
  font-family: var(--yc-font);
  font-weight: 600;
}

body.course-page--yc tbody tr:hover,
body.course-page--yc tbody tr:nth-child(even):hover {
  background: var(--rm-surface2);
}

body.course-page--yc tbody tr:nth-child(even) {
  background: rgba(15, 110, 86, 0.04);
}

body.course-page--yc .ex-card,
body.course-page--yc .quiz-card,
body.course-page--yc .learn-card,
body.course-page--yc .ba-card {
  border-radius: var(--course-radius-sm);
  border-color: var(--rm-border);
  box-shadow: var(--course-shadow);
}

body.course-page--yc .formula {
  background: linear-gradient(145deg, #0c2340, #132f52);
  border-radius: var(--course-radius-sm);
  border: 1px solid var(--rm-border);
  box-shadow: var(--course-shadow);
}

body.course-page--yc .formula .f-eq {
  color: #4dd4b0;
}

body.course-page--yc .quiz-item {
  background: var(--rm-surface);
  border-color: var(--rm-border);
  border-radius: var(--course-radius-sm);
  box-shadow: var(--course-shadow);
}

body.course-page--yc .quiz-opt {
  border-radius: 8px;
}

body.course-page--yc .quiz-opt:hover {
  background: var(--rm-surface2);
  border-color: var(--rm-border);
}

body.course-page--yc .quiz-explanation {
  background: var(--rm-surface2);
  border-radius: 0 8px 8px 0;
  color: var(--rm-text);
}

body.course-page--yc .iq-q {
  background: var(--rm-surface);
  color: var(--rm-text);
  border-bottom: 1px solid var(--rm-border);
  font-family: var(--yc-font);
}

body.course-page--yc .iq-q:hover {
  background: var(--rm-surface2);
}

body.course-page--yc .tag {
  font-family: var(--yc-font);
  border-radius: 999px;
  font-weight: 600;
}

body.course-page--yc .ba-box {
  border-radius: var(--course-radius-sm);
  border: 1px solid var(--rm-border);
  overflow: hidden;
  box-shadow: var(--course-shadow);
}

body.course-page--yc .ba-body {
  background: var(--rm-surface2);
}

body.course-page--yc .divider {
  border-top-color: var(--rm-border);
}

body.course-page--yc .iq-item {
  border-radius: var(--course-radius-sm);
  border-color: var(--rm-border);
  overflow: hidden;
}

body.course-page--yc .iq-a {
  background: var(--rm-surface2);
  border-top-color: var(--rm-border);
}

body.course-page--yc #top-btn {
  background: var(--course-teal);
  color: #fff;
  border: none;
  border-radius: 999px;
  box-shadow: 0 4px 16px rgba(15, 110, 86, 0.35);
}

body.course-page--yc #top-btn:hover {
  background: #0d8064;
  color: #fff;
}

[data-theme="dark"] body.course-page--yc #sidebar {
  background: var(--rm-surface);
  border-right-color: var(--rm-border);
}

[data-theme="dark"] body.course-page--yc .sidebar-title {
  color: var(--rm-text);
}

[data-theme="dark"] body.course-page--yc .nav-item:hover {
  background: var(--rm-surface2);
}

[data-theme="dark"] body.course-page--yc .nav-item.active {
  background: rgba(63, 185, 80, 0.12);
  color: var(--rm-done);
  border-left-color: var(--rm-done);
}

[data-theme="dark"] body.course-page--yc .yc-lecture-stat {
  background: var(--rm-surface);
  border-color: var(--rm-border);
}

[data-theme="dark"] body.course-page--yc .chip-teal {
  background: rgba(63, 185, 80, 0.15);
  color: #3fb950;
  border-color: rgba(63, 185, 80, 0.25);
}

@media (max-width: 900px) {
  body.course-page--yc .yc-lecture-hero {
    padding: 2rem 1.25rem 2rem;
  }

  body.course-page--yc .yc-lecture-stats {
    grid-template-columns: repeat(2, 1fr);
    max-width: 100%;
  }

  body.course-page--yc .content {
    padding-bottom: 4rem;
  }

  body.course-page--yc #sidebar.course-toc-drawer,
  body.course-page--yc #course-toc-drawer {
    background: var(--rm-surface) !important;
    color: var(--rm-text) !important;
    border-right: 1px solid var(--rm-border) !important;
    box-shadow: var(--course-shadow-lg) !important;
  }
}

@media (max-width: 520px) {
  body.course-page--yc .yc-lecture-stats {
    grid-template-columns: 1fr 1fr;
  }
}

/* ── Layout B: ML Features (wrapper / section cards) ── */
body.course-page--yc {
  --color-background-primary: var(--rm-surface);
  --color-background-secondary: var(--rm-surface2);
  --color-background-tertiary: var(--rm-bg);
  --color-border-tertiary: var(--rm-border);
  --color-border-secondary: var(--rm-border);
  --color-text-primary: var(--rm-text);
  --color-text-secondary: var(--rm-muted);
  --border-radius-lg: var(--course-radius);
  --border-radius-md: var(--course-radius-sm);
}

body.course-page--yc .wrapper {
  max-width: 900px;
  margin-left: auto;
  margin-right: auto;
  padding-left: clamp(1rem, 3vw, 2.5rem);
  padding-right: clamp(1rem, 3vw, 2.5rem);
  padding-bottom: 4rem;
}

body.course-page--yc .highlight-box {
  border-radius: 0 var(--course-radius-sm) var(--course-radius-sm) 0;
  box-shadow: none;
}

body.course-page--yc .wrapper > .cover.yc-lecture-hero {
  text-align: left;
  border: none;
  border-radius: 0;
  margin: 0 calc(-1 * clamp(1rem, 3vw, 2.5rem)) 1.5rem;
  padding: 2.5rem clamp(1rem, 3vw, 2.5rem) 2.25rem;
  background: var(--rm-bg);
  border-bottom: 1px solid var(--rm-border);
  position: relative;
  overflow: hidden;
}

body.course-page--yc .wrapper > .cover.yc-lecture-hero::before {
  top: 0;
  left: 0;
  right: 0;
  height: 100%;
  background:
    radial-gradient(ellipse 80% 60% at 20% 10%, rgba(15, 110, 86, 0.2), transparent),
    radial-gradient(ellipse 60% 50% at 80% 80%, rgba(184, 134, 11, 0.12), transparent);
}

body.course-page--yc .wrapper .yc-lecture-hero h1 {
  font-family: var(--yc-font);
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  color: var(--rm-text);
  margin-bottom: 0;
}

body.course-page--yc .wrapper .yc-lecture-hero h1 span {
  color: var(--course-teal);
}

body.course-page--yc .section {
  border-radius: var(--course-radius-sm);
  border: 1px solid var(--rm-border);
  box-shadow: none;
  background: var(--rm-surface);
  padding: 1.75rem;
  margin-bottom: 1rem;
}

body.course-page--yc .wrapper h3,
body.course-page--yc .wrapper .section-title {
  font-family: var(--yc-font);
}

/* Legacy rainbow classes → unified teal */
body.course-page--yc .wrapper [class*="n-"],
body.course-page--yc .wrapper .section-num {
  background: var(--course-teal-lt) !important;
  color: var(--course-teal) !important;
}

body.course-page--yc .wrapper .highlight-box,
body.course-page--yc .wrapper .highlight-box.teal,
body.course-page--yc .wrapper .highlight-box.coral,
body.course-page--yc .wrapper .highlight-box.amber,
body.course-page--yc .wrapper .highlight-box.green {
  background: var(--rm-surface2) !important;
  border-left-color: var(--course-teal) !important;
  box-shadow: none;
}

body.course-page--yc .wrapper .highlight-box.red {
  background: #fdf6f6 !important;
  border-left-color: #c45c5c !important;
}

body.course-page--yc .wrapper .highlight-box strong {
  color: var(--course-teal) !important;
}

body.course-page--yc .wrapper .highlight-box.red strong {
  color: #a32d2d !important;
}

body.course-page--yc .wrapper .flow-box,
body.course-page--yc .wrapper .flow-box.purple,
body.course-page--yc .wrapper .flow-box.coral {
  background: var(--rm-surface) !important;
  color: var(--rm-text) !important;
  border-color: var(--rm-border) !important;
}

body.course-page--yc .wrapper .flow-box.teal {
  background: var(--course-teal-lt) !important;
  color: var(--course-teal) !important;
  border-color: rgba(15, 110, 86, 0.25) !important;
}

body.course-page--yc .wrapper .badge,
body.course-page--yc .wrapper .b-purple,
body.course-page--yc .wrapper .b-blue,
body.course-page--yc .wrapper .b-amber,
body.course-page--yc .wrapper .b-neutral {
  background: var(--rm-surface2) !important;
  color: var(--rm-muted) !important;
}

body.course-page--yc .wrapper .b-good {
  background: var(--course-teal-lt) !important;
  color: var(--course-teal) !important;
}

body.course-page--yc .wrapper .b-bad {
  background: #fcebeb !important;
  color: #a32d2d !important;
}

body.course-page--yc .wrapper .summary-card .num {
  color: var(--course-teal) !important;
}

body.course-page--yc .wrapper .matrix-visual .header-row,
body.course-page--yc .wrapper .matrix-visual .target-col {
  color: var(--course-teal) !important;
}

body.course-page--yc .section-header {
  border-bottom-color: var(--rm-border);
}

body.course-page--yc .section-title {
  font-family: var(--yc-font);
  font-weight: 700;
  letter-spacing: -0.01em;
}

body.course-page--yc .section-num {
  border-radius: 10px;
  font-family: var(--yc-font);
  font-weight: 700;
}

body.course-page--yc .toc {
  background: var(--rm-surface2);
  border-color: var(--rm-border);
  border-radius: var(--course-radius-sm);
}

body.course-page--yc .toc-item {
  border-bottom-color: var(--rm-border);
}

body.course-page--yc th {
  background: var(--course-teal);
  color: #fff;
  border-color: var(--rm-border);
  font-family: var(--yc-font);
}

body.course-page--yc td {
  border-color: var(--rm-border);
}

body.course-page--yc tr:nth-child(even) td {
  background: rgba(15, 110, 86, 0.04);
}

body.course-page--yc .highlight-box {
  border-radius: 0 var(--course-radius-sm) var(--course-radius-sm) 0;
  box-shadow: var(--course-shadow);
}

body.course-page--yc .card-sm,
body.course-page--yc .analogy-card,
body.course-page--yc .mistake-item,
body.course-page--yc .quiz-item,
body.course-page--yc .practice-item,
body.course-page--yc .summary-card,
body.course-page--yc .flow-diagram {
  border-radius: var(--course-radius-sm);
  border-color: var(--rm-border);
  box-shadow: none;
  background: var(--rm-surface2);
}

body.course-page--yc .flow-box {
  border-radius: 8px;
}

body.course-page--yc .badge {
  border-radius: 999px;
  font-family: var(--yc-font);
  font-weight: 600;
}

/* ── Layout C: page-header lectures — Brand Kit owns gradient; shell does not cream-override ── */
body.course-page--yc .page-header.yc-lecture-hero {
  background: linear-gradient(135deg, var(--teal-800) 0%, var(--blue-900) 55%, var(--purple-800) 100%);
  color: #fff;
  text-align: center;
  position: relative;
  overflow: hidden;
  border-bottom: none;
}

body.course-page--yc .page-header.yc-lecture-hero::before,
body.course-page--yc .page-header.yc-lecture-hero::after {
  display: none;
}

body.course-page--yc .page-header .yc-lecture-hero-inner {
  position: relative;
  z-index: 1;
  max-width: 900px;
  margin: 0 auto;
}

body.course-page--yc .page-header.yc-lecture-hero .yc-lecture-eyebrow {
  color: rgba(255, 255, 255, 0.85);
}

body.course-page--yc .page-header.yc-lecture-hero h1,
body.course-page--yc .page-header.yc-lecture-hero .subtitle {
  color: #fff;
  max-width: none;
}

body.course-page--yc .header-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
  justify-content: center;
  margin-top: 1.5rem;
  opacity: 0.9;
  font-size: 0.82rem;
}

body.course-page--yc .page-header.yc-lecture-hero .header-meta span {
  padding: 0.45rem 0.85rem;
  background: rgba(255, 255, 255, 0.12);
  border: 1px solid rgba(255, 255, 255, 0.22);
  border-radius: 999px;
  color: rgba(255, 255, 255, 0.92);
  font-weight: 500;
}

body.course-page--yc .toc-card {
  background: var(--rm-surface) !important;
  border: 1px solid var(--rm-border) !important;
  border-radius: var(--course-radius-sm) !important;
  box-shadow: none !important;
  padding: 1.75rem !important;
  margin-bottom: 1rem;
}

body.course-page--yc .toc-card h2 {
  font-family: var(--yc-font);
  color: var(--rm-muted) !important;
}

body.course-page--yc .toc-grid a {
  border-radius: 8px;
  transition: background 0.15s;
}

body.course-page--yc .toc-grid a:hover {
  background: var(--rm-surface2);
}

body.course-page--yc .part-header {
  border-bottom-color: var(--rm-border) !important;
}

body.course-page--yc .part-title-wrap h2 {
  font-family: var(--yc-font);
  font-weight: 800;
  letter-spacing: -0.02em;
}

body.course-page--yc .card {
  background: var(--rm-surface) !important;
  border-color: var(--rm-border) !important;
  border-radius: var(--course-radius-sm) !important;
  box-shadow: var(--course-shadow) !important;
}

body.course-page--yc .pipeline-lab {
  background: var(--rm-surface) !important;
  border-color: var(--rm-border) !important;
  border-radius: var(--course-radius) !important;
  box-shadow: var(--course-shadow) !important;
}

body.course-page--yc .pipeline-lab-title {
  font-family: var(--yc-font);
  color: var(--rm-text) !important;
}

body.course-page--yc .pipeline-lab-hint {
  color: var(--rm-muted) !important;
}

body.course-page--yc .box,
body.course-page--yc .info-box,
body.course-page--yc .warn-box,
body.course-page--yc .tip-box,
body.course-page--yc .quiz-card,
body.course-page--yc .learn-card {
  border-radius: var(--course-radius-sm);
  border-color: var(--rm-border);
  box-shadow: none;
  background: var(--rm-surface2);
}

/* Layout D: ML Data Processing */
body.course-page--yc #main .section {
  background: var(--rm-surface);
  border: 1px solid var(--rm-border);
  border-radius: var(--course-radius-sm);
  padding: 1.75rem;
  margin-bottom: 1rem;
  box-shadow: none;
}

body.course-page--yc #main .hero {
  background: var(--rm-bg) !important;
  color: var(--rm-text) !important;
  border-bottom: 1px solid var(--rm-border);
}

/* Layout E: Linear Regression page sections */
body.course-page--yc .page {
  max-width: 900px;
  margin-left: auto;
  margin-right: auto;
  padding: 0 clamp(1rem, 3vw, 2.5rem) 4rem;
}

body.course-page--yc .page > div[id^="s"] {
  background: var(--rm-surface);
  border: 1px solid var(--rm-border);
  border-radius: var(--course-radius-sm);
  padding: 1.75rem;
  margin-bottom: 1rem;
  box-shadow: none;
}

body.course-page--yc .sec-header {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  border-bottom: 1px solid var(--rm-border);
  margin-bottom: 1.25rem;
  padding-bottom: 1rem;
}

body.course-page--yc .sec-num {
  min-height: 36px;
  padding: 0 0.75rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--course-teal) !important;
  background: var(--course-teal-lt) !important;
  border-radius: 999px;
  font-family: var(--yc-font);
}

body.course-page--yc .sec-title {
  font-family: var(--yc-font);
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--rm-text);
}

/* ── Layout D: Linear Regression (cover + sticky nav + lr-toc) ── */
body.course-page--yc .cover.yc-lecture-hero {
  min-height: auto !important;
  background: var(--rm-bg) !important;
  color: var(--rm-text) !important;
  text-align: left !important;
  align-items: flex-start !important;
  justify-content: flex-start !important;
  padding: 3.5rem 1.5rem 3rem !important;
  border-bottom: 1px solid var(--rm-border);
}

body.course-page--yc .cover.yc-lecture-hero::before {
  background:
    radial-gradient(ellipse 80% 60% at 20% 10%, rgba(15, 110, 86, 0.2), transparent),
    radial-gradient(ellipse 60% 50% at 80% 80%, rgba(184, 134, 11, 0.12), transparent) !important;
}

body.course-page--yc .cover.yc-lecture-hero .yc-lecture-hero-inner {
  position: relative;
  z-index: 1;
  max-width: 900px;
  width: 100%;
  margin: 0 auto;
}

body.course-page--yc .cover.yc-lecture-hero h1 {
  font-family: var(--yc-font) !important;
  font-size: clamp(2rem, 5vw, 3.25rem) !important;
  font-weight: 800 !important;
  letter-spacing: -0.03em !important;
  color: var(--rm-text) !important;
  text-align: left;
}

body.course-page--yc .cover.yc-lecture-hero h1 span {
  color: var(--course-teal) !important;
}

body.course-page--yc .cover-sub {
  color: var(--rm-muted) !important;
  text-align: left;
  font-size: clamp(1rem, 2vw, 1.15rem);
  line-height: 1.6;
  max-width: 52ch;
}

body.course-page--yc .cover-meta {
  justify-content: flex-start !important;
  gap: 0.75rem !important;
  margin-top: 2rem !important;
}

body.course-page--yc .cover-meta > div {
  padding: 0.85rem 1rem;
  background: var(--rm-surface);
  border: 1px solid var(--rm-border);
  border-radius: 12px;
  min-width: 110px;
}

body.course-page--yc .cover-meta span {
  color: var(--rm-muted) !important;
  font-family: var(--yc-font);
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

body.course-page--yc .cover-meta strong {
  color: var(--rm-text) !important;
  font-size: 1rem;
  font-weight: 700;
}

body.course-page--yc .cover-badge {
  margin-top: 1.5rem !important;
  border-color: var(--rm-border) !important;
  color: var(--rm-muted) !important;
  background: var(--rm-surface);
  font-family: var(--yc-font);
  font-weight: 600;
  border-radius: 999px;
}

body.course-page--yc .lr-toc {
  background: var(--rm-surface) !important;
  color: var(--rm-text) !important;
  border: 1px solid var(--rm-border) !important;
  border-radius: var(--course-radius-sm) !important;
  padding: 1.75rem !important;
  margin-bottom: 1rem;
  box-shadow: none !important;
}

body.course-page--yc .lr-toc .toc-title,
body.course-page--yc .lr-toc .toc-part-label {
  color: var(--rm-muted) !important;
  font-family: var(--yc-font);
}

body.course-page--yc .lr-toc .toc-item {
  color: var(--rm-text) !important;
  border-radius: 8px;
}

body.course-page--yc .lr-toc .toc-item:hover {
  background: var(--rm-surface);
}

body.course-page--yc .sticky-nav {
  background: rgba(250, 248, 244, 0.92) !important;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--rm-border) !important;
  color: var(--rm-text) !important;
}

[data-theme="dark"] body.course-page--yc .sticky-nav {
  background: rgba(13, 17, 23, 0.92) !important;
}

body.course-page--yc .sticky-nav-row a,
body.course-page--yc .sticky-nav-row button {
  color: var(--rm-text) !important;
  border: 1px solid var(--rm-border);
  border-radius: 8px;
  background: var(--rm-topbar-btn-bg);
  font-family: var(--yc-font);
  font-weight: 600;
}

body.course-page--yc .sticky-nav-row a:hover,
body.course-page--yc .sticky-nav-row button:hover {
  background: var(--rm-topbar-btn-hover) !important;
  color: var(--rm-text) !important;
}

body.course-page--yc .sticky-part {
  color: var(--course-teal);
  font-weight: 700;
}

body.course-page--yc .sticky-progress {
  background: var(--rm-progress-track);
}

body.course-page--yc .sticky-progress-bar {
  background: var(--course-teal);
}

body.course-page--yc #sidebar.course-toc-drawer {
  background: var(--rm-surface) !important;
  color: var(--rm-text) !important;
  border-right: 1px solid var(--rm-border) !important;
}

body.course-page--yc .course-drawer-title {
  font-family: var(--yc-font);
  color: var(--rm-muted) !important;
  opacity: 1;
}

body.course-page--yc .course-drawer-link {
  color: var(--rm-muted) !important;
  border-bottom-color: var(--rm-border) !important;
  font-family: var(--yc-font);
  border-radius: 0 8px 8px 0;
  margin-right: 0.5rem;
}

body.course-page--yc .course-drawer-link:hover {
  color: var(--rm-text) !important;
  background: var(--rm-surface2);
}

/* Dark mode: layout families */
[data-theme="dark"] body.course-page--yc .section,
[data-theme="dark"] body.course-page--yc .part,
[data-theme="dark"] body.course-page--yc .toc-card,
[data-theme="dark"] body.course-page--yc .lr-toc,
[data-theme="dark"] body.course-page--yc #main .section,
[data-theme="dark"] body.course-page--yc .page > div[id^="s"],
[data-theme="dark"] body.course-page--yc .card,
[data-theme="dark"] body.course-page--yc .card-colored,
[data-theme="dark"] body.course-page--yc .pipeline-lab {
  background: var(--rm-surface) !important;
  border-color: var(--rm-border) !important;
  color: #c9d1d9 !important;
}

[data-theme="dark"] body.course-page--yc .content,
[data-theme="dark"] body.course-page--yc .toc-wrapper,
[data-theme="dark"] body.course-page--yc .wrapper,
[data-theme="dark"] body.course-page--yc #main,
[data-theme="dark"] body.course-page--yc .page {
  background: transparent !important;
  border-color: transparent !important;
}

[data-theme="dark"] body.course-page--yc .part h2,
[data-theme="dark"] body.course-page--yc .part h3,
[data-theme="dark"] body.course-page--yc .part-title-wrap h2 {
  color: #e6edf3 !important;
}

[data-theme="dark"] body.course-page--yc .part p,
[data-theme="dark"] body.course-page--yc .part li {
  color: #c9d1d9 !important;
}

[data-theme="dark"] body.course-page--yc .header-meta span,
[data-theme="dark"] body.course-page--yc .cover-meta > div {
  background: var(--rm-surface);
  border-color: var(--rm-border);
}

[data-theme="dark"] body.course-page--yc .wrapper .section,
[data-theme="dark"] body.course-page--yc .wrapper .toc,
[data-theme="dark"] body.course-page--yc .wrapper .analogy-card,
[data-theme="dark"] body.course-page--yc .wrapper .card-sm,
[data-theme="dark"] body.course-page--yc .wrapper .flow-diagram,
[data-theme="dark"] body.course-page--yc .wrapper .quiz-item,
[data-theme="dark"] body.course-page--yc .wrapper .summary-card {
  background: var(--rm-surface);
  border-color: var(--rm-border);
}

[data-theme="dark"] body.course-page--yc .wrapper .highlight-box,
[data-theme="dark"] body.course-page--yc .wrapper .practice-item,
[data-theme="dark"] body.course-page--yc .wrapper .mistake-item {
  background: var(--rm-surface2) !important;
}

[data-theme="dark"] body.course-page--yc .wrapper th {
  background: #0b6049 !important;
}

[data-theme="dark"] body.course-page--yc .page-header .badge {
  background: rgba(63, 185, 80, 0.15) !important;
  color: var(--rm-done) !important;
  border-color: rgba(63, 185, 80, 0.25) !important;
}

@media (max-width: 900px) {
  body.course-page--yc .wrapper > .cover.yc-lecture-hero {
    margin: 0 -1rem 1.5rem;
    padding: 2.5rem 1rem 2rem;
  }

  body.course-page--yc .page-header.yc-lecture-hero {
    padding: 2.5rem 1rem 2rem !important;
  }

  body.course-page--yc .cover.yc-lecture-hero {
    padding: 2.5rem 1rem 2rem !important;
  }

  body.course-page--yc .page-header h1 {
    max-width: 100%;
  }

  body.course-page--yc .cover-meta {
    flex-wrap: wrap;
  }

  body.course-page--yc .cover-meta > div {
    flex: 1 1 calc(50% - 0.5rem);
    min-width: 0;
  }
}

/* ── Unified FAB dock (Practice + Gemini, bottom-right) ── */
.course-fab-dock {
  position: fixed;
  bottom: calc(var(--course-footer-nav-h, 64px) + 1rem);
  right: 1rem;
  z-index: 9000;
  display: flex;
  flex-direction: column-reverse;
  align-items: flex-end;
  gap: 0.75rem;
  max-width: calc(100vw - 2rem);
}

body.course-page.has-sticky-part-nav .course-fab-dock {
  bottom: calc(var(--course-footer-nav-h, 64px) + var(--course-sticky-nav-h, 0px) + 1rem);
}

@media (min-width: 901px) {
  body.course-page.has-sticky-part-nav .course-fab-dock {
    bottom: calc(var(--course-sticky-nav-h, 0px) + 1rem);
  }
}

.course-fab-dock .gemini-mentor-fab,
.course-fab-dock .practice-lab-fab,
.course-fab-dock .practice-resources-fab {
  position: static;
  bottom: auto;
  right: auto;
  left: auto;
  z-index: auto;
}

/* ── Gemini floating mentor FAB ── */
.gemini-mentor-fab {
  position: fixed;
  bottom: calc(var(--course-footer-nav-h, 64px) + 1rem);
  right: 1rem;
  z-index: 9000;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 0.75rem;
}
body.has-gemini-fab.course-page {
  padding-bottom: calc(var(--course-footer-nav-h) + env(safe-area-inset-bottom, 0px));
}
.gemini-fab-btn,
.practice-fab-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  min-width: var(--course-fab-btn-min-w);
  height: var(--course-fab-btn-h);
  padding: 0 1.1rem;
  box-sizing: border-box;
  border-radius: 999px;
  color: #fff;
  border: none;
  font-family: var(--course-font);
  font-weight: 700;
  font-size: 0.95rem;
  line-height: 1;
  white-space: nowrap;
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
}
.gemini-fab-btn {
  background: linear-gradient(135deg, #0F6E56, #185FA5);
  box-shadow: 0 4px 20px rgba(15, 110, 86, 0.4);
}
.gemini-fab-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 24px rgba(15, 110, 86, 0.5);
}
.practice-lab-fab-btn {
  background: linear-gradient(135deg, #185FA5, #6B4FBB);
  box-shadow: 0 4px 20px rgba(24, 95, 165, 0.35);
}
.practice-lab-fab-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 24px rgba(24, 95, 165, 0.45);
}
.gemini-fab-icon { font-size: 1.1rem; }
.gemini-mentor-panel {
  width: 300px;
  max-width: calc(100vw - 2rem);
  background: var(--rm-surface, #fff);
  border: 1px solid var(--rm-border, #ddd);
  border-radius: var(--course-radius, 14px);
  box-shadow: var(--course-shadow-lg, 0 12px 40px rgba(0,0,0,.12));
  padding: 1rem 1.15rem;
  animation: geminiPanelIn 0.2s ease;
}
.gemini-mentor-panel[hidden] { display: none; }
@keyframes geminiPanelIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}
.gemini-panel-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.35rem;
}
.gemini-panel-title {
  font-size: 1rem;
  margin: 0;
}
.gemini-panel-close {
  background: none;
  border: none;
  font-size: 1.4rem;
  cursor: pointer;
  color: var(--rm-muted);
  line-height: 1;
  padding: 0 0.25rem;
}
.gemini-module-ctx {
  font-size: 0.82rem;
  color: var(--rm-muted);
  margin: 0 0 0.4rem;
}
.gemini-panel-hint {
  font-size: 0.85rem;
  color: var(--rm-muted);
  margin: 0 0 0.75rem;
  line-height: 1.45;
}
.gemini-open-btn {
  width: 100%;
  padding: 0.65rem 1rem;
  background: var(--course-teal, #0F6E56);
  color: #fff;
  border: none;
  border-radius: var(--course-radius-sm, 10px);
  font-family: var(--course-font);
  font-weight: 600;
  cursor: pointer;
  font-size: 0.92rem;
  margin-bottom: 0.75rem;
}
.gemini-open-btn:hover { filter: brightness(1.05); }
.gemini-chips {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  margin-bottom: 0.65rem;
}
.gemini-chip {
  text-align: left;
  padding: 0.45rem 0.7rem;
  background: var(--rm-surface2, #f5f5f5);
  border: 1px solid var(--rm-border, #ddd);
  border-radius: 8px;
  font-family: var(--course-font);
  font-size: 0.8rem;
  cursor: pointer;
  line-height: 1.35;
}
.gemini-chip:hover { border-color: var(--course-teal); }
.gemini-hint {
  font-size: 0.72rem;
  color: var(--rm-muted);
  margin: 0;
  line-height: 1.4;
}
.gemini-copy-toast {
  position: fixed;
  bottom: calc(var(--course-footer-nav-h, 64px) + 5rem);
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: #0C2340;
  color: #fff;
  padding: 0.5rem 1rem;
  border-radius: 8px;
  font-size: 0.85rem;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s, transform 0.2s;
  z-index: 10001;
  max-width: 90vw;
  text-align: center;
}
.gemini-copy-toast.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

@media (max-width: 600px) {
  .course-fab-dock {
    right: 0.75rem;
    left: 0.75rem;
    align-items: stretch;
  }

  .course-fab-dock .gemini-mentor-fab,
  .course-fab-dock .practice-lab-fab,
  .course-fab-dock .practice-resources-fab {
    align-items: stretch;
  }

  .course-fab-dock .gemini-mentor-panel,
  .course-fab-dock .practice-lab-panel,
  .course-fab-dock .practice-fab-panel {
    width: 100%;
    max-width: none;
  }

  .course-fab-dock .gemini-fab-btn,
  .course-fab-dock .practice-lab-fab-btn,
  .course-fab-dock .practice-fab-btn {
    align-self: flex-end;
  }

  .gemini-mentor-fab {
    right: 0.75rem;
    left: 0.75rem;
    align-items: stretch;
  }
  .gemini-mentor-panel {
    width: 100%;
    max-width: none;
  }
  .gemini-fab-btn {
    align-self: flex-end;
  }
}

/* ── Per-section context capsule buttons ── */
.part-header,
.section-header {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}
.part-title-wrap {
  flex: 1;
  min-width: 0;
}
.ds-section-capsule {
  margin-left: auto;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
  border: 1px solid var(--course-teal, #0F6E56);
  background: var(--course-teal-lt, #E1F5EE);
  color: var(--course-teal, #0F6E56);
  font-family: var(--course-font);
  font-size: 0.78rem;
  font-weight: 700;
  cursor: pointer;
  flex-shrink: 0;
  transition: background 0.15s, color 0.15s, transform 0.15s;
}
.ds-section-capsule:hover {
  background: var(--course-teal, #0F6E56);
  color: #fff;
  transform: translateY(-1px);
}
.ds-capsule-icon {
  font-size: 0.85rem;
  line-height: 1;
}
[data-theme="dark"] .ds-section-capsule {
  background: rgba(63, 185, 80, 0.12);
  border-color: #3fb950;
  color: #3fb950;
}
[data-theme="dark"] .ds-section-capsule:hover {
  background: #3fb950;
  color: #0d1117;
}

.ds-section-colab {
  border-color: var(--course-amber, #9A6700);
  background: rgba(154, 103, 0, 0.08);
  color: var(--course-amber, #9A6700);
}
.ds-section-colab:hover {
  background: var(--course-amber, #9A6700);
  color: #fff;
}
[data-theme="dark"] .ds-section-colab {
  background: rgba(217, 180, 106, 0.12);
  border-color: #d9b46a;
  color: #d9b46a;
}
[data-theme="dark"] .ds-section-colab:hover {
  background: #d9b46a;
  color: #0d1117;
}

.ds-section-practice {
  border-color: var(--course-teal, #185FA5);
  background: rgba(24, 95, 165, 0.08);
  color: var(--course-teal, #185FA5);
}
.ds-section-practice:hover {
  background: var(--course-teal, #185FA5);
  color: #fff;
}
[data-theme="dark"] .ds-section-practice {
  background: rgba(95, 208, 194, 0.12);
  border-color: #5fd0c2;
  color: #5fd0c2;
}
[data-theme="dark"] .ds-section-practice:hover {
  background: #5fd0c2;
  color: #0d1117;
}

/* ── Context capsule block (inside Gemini panel) ── */
.gemini-capsule-block {
  margin-bottom: 0.75rem;
}
.gemini-capsule-label {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--rm-muted);
  margin: 0 0 0.25rem;
}
.gemini-capsule-section {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--rm-text);
  margin: 0 0 0.65rem;
  line-height: 1.4;
}
.gemini-capsule-send {
  width: 100%;
  padding: 0.65rem 1rem;
  background: linear-gradient(135deg, #0F6E56, #185FA5);
  color: #fff;
  border: none;
  border-radius: var(--course-radius-sm, 10px);
  font-family: var(--course-font);
  font-weight: 600;
  cursor: pointer;
  font-size: 0.9rem;
  margin-bottom: 0.65rem;
}
.gemini-capsule-send:hover {
  filter: brightness(1.05);
}
.gemini-capsule-steps {
  margin: 0;
  padding-left: 1.15rem;
  font-size: 0.78rem;
  color: var(--rm-muted);
  line-height: 1.5;
}
.gemini-capsule-steps kbd {
  font-family: var(--course-mono, monospace);
  font-size: 0.72rem;
  padding: 0.1rem 0.35rem;
  border-radius: 4px;
  border: 1px solid var(--rm-border);
  background: var(--rm-surface2);
}
.gemini-fab-pulse {
  animation: geminiFabPulse 1.2s ease-in-out 3;
}
@keyframes geminiFabPulse {
  0%, 100% { box-shadow: 0 4px 20px rgba(15, 110, 86, 0.4); }
  50% { box-shadow: 0 4px 28px rgba(15, 110, 86, 0.85), 0 0 0 6px rgba(15, 110, 86, 0.2); }
}

/* ── Practice resources floating FAB ── */
.practice-resources-fab {
  position: fixed;
  bottom: calc(var(--course-footer-nav-h, 64px) + 1rem);
  right: 1rem;
  z-index: 9000;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 0.75rem;
}

.practice-fab-btn {
  background: linear-gradient(135deg, #534AB7, #0F6E56);
  box-shadow: 0 4px 20px rgba(83, 74, 183, 0.35);
}

.practice-fab-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 24px rgba(83, 74, 183, 0.45);
}

.practice-fab-icon {
  display: flex;
  width: 1.1rem;
  height: 1.1rem;
}

.practice-fab-icon svg {
  width: 100%;
  height: 100%;
}

.practice-fab-panel {
  width: 320px;
  max-width: calc(100vw - 2rem);
  background: var(--rm-surface, #fff);
  border: 1px solid var(--rm-border, #ddd);
  border-radius: var(--course-radius, 14px);
  box-shadow: var(--course-shadow-lg, 0 12px 40px rgba(0,0,0,.12));
  padding: 1rem 1.15rem;
  animation: practicePanelIn 0.2s ease;
}

.practice-fab-panel[hidden] { display: none; }

@keyframes practicePanelIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

.practice-fab-panel-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.35rem;
}

.practice-fab-panel-title {
  font-size: 1rem;
  margin: 0;
}

.practice-fab-panel-close {
  background: none;
  border: none;
  font-size: 1.4rem;
  cursor: pointer;
  color: var(--rm-muted);
  line-height: 1;
  padding: 0 0.25rem;
}

.practice-fab-module-ctx {
  font-size: 0.82rem;
  color: var(--rm-muted);
  margin: 0 0 0.25rem;
}

.practice-fab-panel-hint {
  font-size: 0.8rem;
  color: var(--rm-muted);
  margin: 0 0 0.75rem;
}

.practice-fab-list {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.practice-fab-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 0.85rem;
  border-radius: 10px;
  border: 1px solid var(--rm-border, #e0e0e0);
  background: var(--rm-surface2, #f7f5f0);
  color: inherit;
  text-decoration: none;
  transition: border-color 0.2s, box-shadow 0.2s, transform 0.15s;
}

.practice-fab-item:hover {
  border-color: #534AB7;
  box-shadow: 0 4px 16px rgba(83, 74, 183, 0.12);
  transform: translateY(-1px);
}

.practice-fab-item__icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  flex-shrink: 0;
  border-radius: 8px;
  color: #fff;
}

.practice-fab-item__icon svg {
  width: 20px;
  height: 20px;
}

.practice-fab-item__icon--dataset {
  background: linear-gradient(135deg, #534AB7, #0F6E56);
}

.practice-fab-item__icon--notebook {
  background: linear-gradient(135deg, #185FA5, #534AB7);
}

.practice-fab-item__body {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
}

.practice-fab-item__badge {
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: #534AB7;
}

.practice-fab-item__title {
  font-size: 0.9rem;
  font-weight: 600;
  line-height: 1.3;
}

.practice-fab-item__meta {
  font-size: 0.72rem;
  color: var(--rm-muted);
  font-family: var(--course-mono, monospace);
}

.practice-fab-item__desc {
  font-size: 0.78rem;
  color: var(--rm-muted);
  line-height: 1.35;
}

.practice-fab-item__cta {
  flex-shrink: 0;
  padding: 0.35rem 0.7rem;
  border-radius: 999px;
  background: #534AB7;
  color: #fff;
  font-size: 0.75rem;
  font-weight: 600;
  white-space: nowrap;
}

@media (max-width: 600px) {
  .practice-resources-fab {
    right: 0.75rem;
    left: auto;
  }

  .practice-fab-btn {
    align-self: flex-end;
  }
}

@media (max-width: 480px) {
  .practice-fab-item {
    flex-wrap: wrap;
  }

  .practice-fab-item__cta {
    width: 100%;
    text-align: center;
  }
}

[data-theme="dark"] .practice-fab-panel {
  background: #161b22;
  border-color: #30363d;
}

[data-theme="dark"] .practice-fab-item {
  background: #21262d;
  border-color: #30363d;
}

[data-theme="dark"] .practice-fab-item:hover {
  border-color: #534AB7;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.35);
}

[data-theme="dark"] .practice-fab-item__badge {
  color: #bc8cff;
}

[data-theme="dark"] .practice-fab-item__title {
  color: #e6edf3;
}

[data-theme="dark"] .practice-fab-item__meta,
[data-theme="dark"] .practice-fab-item__desc,
[data-theme="dark"] .practice-fab-module-ctx,
[data-theme="dark"] .practice-fab-panel-hint {
  color: #8b949e;
}

[data-theme="dark"] .practice-fab-panel-title {
  color: #e6edf3;
}

/* ── Landing login modal (index.html) ── */
.landing-auth-overlay {
  position: fixed;
  inset: 0;
  background: rgba(8, 10, 18, 0.72);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 9999;
  padding: 1rem;
}

[data-theme="light"] .landing-auth-overlay {
  background: rgba(248, 250, 252, 0.82);
}

.landing-auth-overlay.is-open {
  display: flex;
}

.landing-auth-card {
  width: min(420px, 100%);
  background: #161b22;
  border: 1px solid #30363d;
  border-radius: 14px;
  padding: 1.5rem 1.25rem;
  color: #e6edf3;
  text-align: center;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.45);
}

[data-theme="light"] .landing-auth-card {
  background: #ffffff;
  border-color: rgba(12, 35, 64, 0.12);
  color: #1a1a18;
  box-shadow: 0 20px 50px rgba(12, 35, 64, 0.12);
}

.landing-auth-card h3 {
  margin: 0 0 0.45rem;
  font-size: 1.2rem;
  font-weight: 700;
  color: inherit;
}

.landing-auth-card p {
  margin: 0 0 1rem;
  color: #8b949e;
  font-size: 0.92rem;
  line-height: 1.5;
}

[data-theme="light"] .landing-auth-card p {
  color: #5a5a56;
}

.landing-auth-origin-hint {
  margin: 0 0 0.85rem;
  padding: 0.55rem 0.65rem;
  border-radius: 8px;
  background: rgba(226, 137, 107, 0.12);
  border: 1px solid rgba(226, 137, 107, 0.35);
  color: #e2896b;
  font-size: 0.85rem;
}

[data-theme="light"] .landing-auth-origin-hint {
  background: rgba(154, 103, 0, 0.08);
  border-color: rgba(154, 103, 0, 0.28);
  color: #9A6700;
}

#landing-auth-btn {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 44px;
}

/* Hub navbar Skillio wordmark (index.html, ostad-course.html) */
.course-hub-nav-brand--skillio {
  text-decoration: none;
  flex-shrink: 0;
}

.course-hub-nav-brand--skillio .course-hub-nav-logo {
  display: inline-flex;
  align-items: baseline;
  font-family: 'Kalam', cursive;
  font-weight: 700;
  font-size: 1.4rem;
  line-height: 1;
  letter-spacing: -0.01em;
}

.course-hub-nav-brand--skillio .course-hub-nav-logo-skill {
  color: var(--rm-text);
}

[data-theme="light"] .course-hub-nav-brand--skillio .course-hub-nav-logo-skill {
  color: #1a1a18;
}

.course-hub-nav-brand--skillio .course-hub-nav-logo-io {
  background: linear-gradient(90deg, #5fd0c2, #d9b46a);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.course-hub-nav-brand--skillio:hover .course-hub-nav-logo {
  opacity: 0.9;
}

.course-hub-back-link {
  display: flex;
  width: 100%;
  justify-content: flex-start;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--rm-muted);
  text-decoration: none;
  margin-bottom: 0.75rem;
  font-family: var(--yc-font, 'Inter', sans-serif);
  transition: color 0.15s;
  text-align: left;
}

.course-hub-back-link:hover {
  color: var(--course-teal);
}

.course-hub-footer-link {
  color: var(--rm-muted);
  text-decoration: none;
  transition: color 0.15s;
}

.course-hub-footer-link:hover {
  color: var(--course-teal);
}