:root {
  --sidebar-width: 280px;
  --bg: #0d1117;
  --sidebar-bg: #161b22;
  --card-bg: #21262d;
  --text: #f0f6fc;
  --muted: #8b949e;
  --accent: #58a6ff;
  --accent-soft: rgba(88, 166, 255, 0.12);
  --border: #30363d;
  --shadow: 0 12px 40px rgba(0, 0, 0, 0.35);
  --radius: 12px;
  --transition: 0.25s ease;
}

/* Light theme (learn hubs) */
[data-theme="light"] {
  --bg: #f8fafc;
  --sidebar-bg: #0f172a;
  --card-bg: #ffffff;
  --text: #0f172a;
  --muted: #64748b;
  --accent: #3b82f6;
  --accent-soft: rgba(59, 130, 246, 0.1);
  --border: #e2e8f0;
  --shadow: 0 10px 30px rgba(15, 23, 42, 0.08);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  min-height: 100vh;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

/* Sidebar */
.sidebar {
  width: var(--sidebar-width);
  background: var(--sidebar-bg);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  position: fixed;
  inset: 0 auto 0 0;
  z-index: 100;
  overflow-y: auto;
  transition: transform var(--transition);
}

.sidebar-header {
  padding: 1.5rem 1.25rem 1rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.sidebar-header .brand {
  color: var(--accent);
  font-weight: 700;
  font-size: 0.95rem;
  letter-spacing: 0.04em;
}

.sidebar-header .sub {
  color: #94a3b8;
  font-size: 0.75rem;
  margin-top: 0.35rem;
}

.nav-links {
  list-style: none;
  padding: 0.75rem 0 1.5rem;
  flex: 1;
}

.nav-item {
  padding: 0.7rem 1.25rem;
  cursor: pointer;
  color: #94a3b8;
  display: flex;
  align-items: center;
  gap: 0.65rem;
  transition: background var(--transition), color var(--transition);
  border-right: 3px solid transparent;
  font-size: 0.92rem;
}

.nav-item:hover {
  background: var(--accent-soft);
  color: #e2e8f0;
}

.nav-item.active {
  background: var(--accent-soft);
  color: var(--accent);
  border-right-color: var(--accent);
}

.nav-group-label {
  padding: 1rem 1.25rem 0.35rem;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: #64748b;
}

/* Main */
.main {
  margin-left: var(--sidebar-width);
  flex: 1;
  min-width: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem 1.75rem;
  border-bottom: 1px solid var(--border);
  background: color-mix(in srgb, var(--card-bg) 88%, transparent);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 50;
}

.topbar h1 {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.hamburger {
  display: none;
  background: none;
  border: none;
  color: var(--text);
  font-size: 1.5rem;
  cursor: pointer;
}

.breadcrumb {
  display: none;
  align-items: center;
  gap: 0.4rem;
  padding: 0.65rem 1.75rem;
  font-size: 0.82rem;
  color: var(--muted);
  border-bottom: 1px solid var(--border);
  background: var(--card-bg);
}

.breadcrumb.visible {
  display: flex;
}

.breadcrumb a {
  color: var(--accent);
  cursor: pointer;
  text-decoration: none;
  font-weight: 500;
}

.breadcrumb a:hover {
  text-decoration: underline;
}

.content {
  padding: 2rem 1.75rem 3rem;
  max-width: 1100px;
  width: 100%;
  margin: 0 auto;
}

section.panel {
  display: none;
  animation: fadeIn 0.35s ease;
}

section.panel.active {
  display: block;
}

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

h2.section-title {
  font-size: 1.75rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 0.5rem;
  padding-bottom: 0.85rem;
  border-bottom: 1px solid var(--border);
}

.section-desc {
  color: var(--muted);
  margin: 1rem 0 1.75rem;
  max-width: 46rem;
}

/* Hero */
.hero {
  background: linear-gradient(135deg, #0f172a 0%, #1e3a5f 45%, #2563eb 100%);
  color: #f8fafc;
  border-radius: 16px;
  padding: 2.25rem;
  margin-bottom: 1.75rem;
  box-shadow: var(--shadow);
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.hero .pill {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  background: rgba(255, 255, 255, 0.14);
  border: 1px solid rgba(255, 255, 255, 0.25);
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
  margin-bottom: 1rem;
}

.hero h2 {
  font-size: 1.85rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 0.75rem;
  border: none;
  padding: 0;
}

.hero p {
  opacity: 0.95;
  max-width: 42rem;
  font-size: 1.02rem;
  line-height: 1.7;
}

.intro-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1.75rem;
  box-shadow: var(--shadow);
}

.intro-card p {
  color: var(--muted);
}

/* Stats */
.stats-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 1rem;
  margin-bottom: 1.75rem;
}

.stat-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.1rem;
  text-align: center;
}

.stat-card[data-jump] {
  cursor: pointer;
  transition: border-color var(--transition), transform var(--transition);
}

.stat-card[data-jump]:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
}

.stat-card .n {
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--accent);
}

.stat-card .l {
  font-size: 0.82rem;
  color: var(--muted);
  margin-top: 0.2rem;
}

/* Grids / cards */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 1rem;
  margin-bottom: 1.75rem;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  transition: transform var(--transition), border-color var(--transition);
  cursor: pointer;
}

.card:hover {
  transform: translateY(-3px);
  border-color: var(--accent);
}

.card h3 {
  color: var(--accent);
  font-size: 1rem;
  margin-bottom: 0.5rem;
}

.card p {
  color: var(--muted);
  font-size: 0.9rem;
}

/* Focus areas: informational only — no click/hover affordance */
.topic-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: var(--radius);
  padding: 1.25rem;
  cursor: default;
  pointer-events: none;
  user-select: text;
}

.topic-card:hover,
.topic-card:focus {
  transform: none;
  border-color: var(--border);
  border-left-color: var(--accent);
  box-shadow: none;
}

.topic-card h3 {
  color: var(--accent);
  font-size: 1rem;
  margin-bottom: 0.5rem;
}

.topic-card p {
  color: var(--muted);
  font-size: 0.9rem;
}

/* Visuals */
.asset-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1.15rem;
}

.asset-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  cursor: pointer;
  transition: transform var(--transition), border-color var(--transition);
}

.asset-card:hover {
  transform: translateY(-3px);
  border-color: var(--accent);
}

.asset-card .thumb {
  width: 100%;
  aspect-ratio: 16 / 10;
  object-fit: cover;
  background: #111;
  display: block;
}

.asset-card .thumb.missing {
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--muted);
  font-size: 0.85rem;
  background: repeating-linear-gradient(
    45deg,
    #1a1f27,
    #1a1f27 10px,
    #222833 10px,
    #222833 20px
  );
}

[data-theme="light"] .asset-card .thumb.missing {
  background: repeating-linear-gradient(
    45deg,
    #e2e8f0,
    #e2e8f0 10px,
    #f1f5f9 10px,
    #f1f5f9 20px
  );
}

.asset-info {
  padding: 0.9rem 1rem 1.1rem;
}

.asset-info h4 {
  color: var(--accent);
  font-size: 0.95rem;
  margin-bottom: 0.35rem;
}

.asset-info p {
  color: var(--muted);
  font-size: 0.8rem;
}

/* Library */
.library-layout {
  display: grid;
  grid-template-columns: minmax(260px, 340px) minmax(0, 1fr);
  gap: 1rem;
  align-items: stretch;
  height: calc(100vh - 210px);
  min-height: 520px;
}

.library-list {
  height: 100%;
  max-height: none;
  overflow-y: auto;
  overflow-x: hidden;
  padding-right: 0.25rem;
  min-height: 0;
}

.library-reader {
  position: relative;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  height: 100%;
  min-height: 0;
}

.library-reader-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border);
  background: var(--bg);
  font-size: 0.9rem;
  font-weight: 600;
}

.library-reader-bar a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.82rem;
}

#library-frame {
  position: relative;
  z-index: 1;
  width: 100%;
  flex: 1 1 auto;
  border: 0;
  background: #fff;
  min-height: 0;
  height: 100%;
}

.library-reader-empty {
  position: absolute;
  inset: 3.25rem 0 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  color: var(--muted);
  text-align: center;
  pointer-events: none;
  z-index: 2;
}

.library-reader-empty[hidden] {
  display: none !important;
}

.library-open {
  appearance: none;
  background: none;
  border: 0;
  padding: 0;
  color: var(--accent);
  font: inherit;
  font-weight: 600;
  text-align: left;
  cursor: pointer;
}

.library-open:disabled {
  color: var(--text);
  cursor: default;
}

.library-actions {
  display: flex;
  gap: 0.75rem;
  margin-top: 0.35rem;
  font-size: 0.78rem;
}

.library-actions a {
  font-weight: 500;
  opacity: 0.9;
}

.file-item.is-readable {
  cursor: pointer;
}

.file-item.active {
  border-color: var(--accent);
  box-shadow: 0 0 0 1px var(--accent-soft);
}

@media (max-width: 980px) {
  .library-layout {
    grid-template-columns: 1fr;
    height: auto;
    min-height: 0;
  }
  .library-list {
    max-height: 36vh;
    height: auto;
  }
  .library-reader {
    height: 58vh;
    min-height: 420px;
  }
  #library-frame {
    min-height: 0;
  }
}

/* Section header banners */
.section-banner {
  width: 100%;
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--border);
  margin: 0 0 1.15rem;
  background: var(--card-bg);
}

.section-banner img {
  display: block;
  width: 100%;
  height: auto;
  max-height: 220px;
  object-fit: cover;
}

.file-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.file-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1rem 1.15rem;
}

.file-item a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
}

.file-item a:hover {
  text-decoration: underline;
}

.file-item .meta {
  color: var(--muted);
  font-size: 0.82rem;
  margin-top: 0.25rem;
}

.badge {
  font-size: 0.72rem;
  color: var(--muted);
  background: var(--accent-soft);
  border: 1px solid var(--border);
  padding: 0.2rem 0.55rem;
  border-radius: 6px;
  flex-shrink: 0;
}

/* Slideshow */
.slideshow {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 16px;
  overflow: hidden;
  box-shadow: var(--shadow);
  max-width: 960px;
  margin: 0 auto;
  position: relative;
}

.slide {
  display: none;
}

.slide.active {
  display: block;
}

.slide img {
  width: 100%;
  display: block;
  background: #000;
}

.slide .placeholder {
  aspect-ratio: 16 / 9;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--muted);
  background: #111827;
  padding: 2rem;
  text-align: center;
}

.slide-caption {
  padding: 0.9rem 1rem;
  text-align: center;
  border-top: 1px solid var(--border);
  color: #e2e8f0;
  background: rgba(0, 0, 0, 0.55);
  font-size: 0.92rem;
}

[data-theme="light"] .slide-caption {
  background: #0f172a;
  color: #f8fafc;
}

.slide-number {
  position: absolute;
  top: 0.6rem;
  left: 0.6rem;
  background: rgba(0, 0, 0, 0.55);
  color: #fff;
  font-size: 0.75rem;
  padding: 0.25rem 0.55rem;
  border-radius: 6px;
  z-index: 2;
}

.prev,
.next {
  position: absolute;
  top: 45%;
  transform: translateY(-50%);
  background: rgba(0, 0, 0, 0.4);
  color: #fff;
  border: none;
  padding: 0.85rem 0.95rem;
  cursor: pointer;
  font-size: 1.1rem;
  z-index: 2;
  border-radius: 6px;
}

.prev {
  left: 0.5rem;
}

.next {
  right: 0.5rem;
}

.prev:hover,
.next:hover {
  background: rgba(0, 0, 0, 0.75);
}

.dots {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.35rem;
  padding: 0.85rem;
}

.dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: #71717a;
  border: none;
  cursor: pointer;
}

.dot.active {
  background: var(--accent);
}

.deck-download {
  display: inline-block;
  margin: 0 0 1rem;
  color: var(--accent);
  font-weight: 600;
  text-decoration: none;
}

.deck-download:hover {
  text-decoration: underline;
}

/* Media */
.media-block {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  margin-bottom: 1rem;
}

.media-block video,
.media-block audio {
  width: 100%;
  margin-top: 0.75rem;
}

/* Shorts (~30s vertical NotebookLM videos) */
.shorts-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1.25rem;
}

.short-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
}

.short-frame {
  background: #0f172a;
  display: flex;
  align-items: center;
  justify-content: center;
  aspect-ratio: 9 / 16;
  max-height: 420px;
}

.short-frame video {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
  background: #000;
}

.short-body {
  padding: 1rem 1.1rem 1.15rem;
}

.short-badge {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-soft);
  border-radius: 999px;
  padding: 0.2rem 0.55rem;
  margin-bottom: 0.45rem;
}

.short-body h3 {
  font-size: 1rem;
  margin-bottom: 0.35rem;
}

.short-body p {
  font-size: 0.88rem;
  color: var(--muted);
  line-height: 1.45;
}

@media (max-width: 700px) {
  .shorts-grid {
    grid-template-columns: minmax(0, 320px);
    justify-content: center;
  }
}

/* Lightbox */
.lightbox {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.85);
  backdrop-filter: blur(8px);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 2000;
  padding: 1.25rem;
}

.lightbox.active {
  display: flex;
  gap: 0.65rem;
}

.lightbox-panel {
  width: min(1100px, 94vw);
  height: min(85vh, 820px);
  background: var(--sidebar-bg);
  border: 1px solid var(--border);
  border-radius: 16px;
  display: flex;
  overflow: hidden;
  position: relative;
  box-shadow: 0 0 50px rgba(0, 0, 0, 0.5);
}

.lightbox-nav {
  flex-shrink: 0;
  align-self: center;
  width: 2.75rem;
  height: 2.75rem;
  border-radius: 999px;
  border: 1px solid rgba(255, 255, 255, 0.18);
  background: rgba(15, 23, 42, 0.72);
  color: #fff;
  font-size: 1.75rem;
  line-height: 1;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: background 0.15s ease, border-color 0.15s ease;
}

.lightbox-nav:hover {
  background: rgba(37, 99, 235, 0.85);
  border-color: rgba(147, 197, 253, 0.55);
}

.lightbox-counter {
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  margin-bottom: 0.55rem;
}

.lightbox-hint {
  margin-top: 1rem;
  color: #64748b;
  font-size: 0.75rem;
}

.lightbox-img-wrap {
  flex: 4;
  background: #000;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}

.lightbox-img-wrap img {
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
  border-radius: 8px;
  box-shadow: 0 0 30px rgba(88, 166, 255, 0.25);
}

.lightbox-copy {
  flex: 1;
  min-width: 200px;
  max-width: 280px;
  padding: 1.5rem 1.25rem;
  border-left: 1px solid var(--border);
  overflow-y: auto;
}

.lightbox-copy h3 {
  color: var(--accent);
  margin-bottom: 0.65rem;
  font-size: 1.1rem;
}

.lightbox-copy p {
  color: #94a3b8;
  font-size: 0.88rem;
}

.close-lightbox {
  position: absolute;
  top: 0.75rem;
  right: 0.9rem;
  background: none;
  border: none;
  color: #94a3b8;
  font-size: 1.75rem;
  cursor: pointer;
  line-height: 1;
  z-index: 2;
}

.close-lightbox:hover {
  color: #fff;
}

/* Footer meta */
.site-footer {
  margin-top: 2.5rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.82rem;
}

.site-footer a {
  color: var(--accent);
}

.overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  z-index: 90;
}

.overlay.show {
  display: block;
}

/* Mobile */
@media (max-width: 860px) {
  .sidebar {
    transform: translateX(-100%);
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .main {
    margin-left: 0;
  }

  .hamburger {
    display: block;
  }

  .lightbox-panel {
    flex-direction: column;
    height: auto;
    max-height: 90vh;
  }

  .lightbox-img-wrap {
    flex: none;
    min-height: 45vh;
  }

  .lightbox-copy {
    max-width: none;
    border-left: none;
    border-top: 1px solid var(--border);
  }
}