:root {
  --cp-bg: #1A1A2E;
  --cp-panel: #261817;
  --cp-panel-2: #2A2A3E;
  --cp-border: rgba(255, 255, 255, 0.08);
  --cp-border-strong: rgba(255, 255, 255, 0.14);
  --cp-accent: #FF6363;
  --cp-accent-deep: #67000E;
  --cp-text: #FFFFFF;
  --cp-text-soft: #CBD5E1;
  --cp-text-muted: #94A3B8;
  --cp-text-dim: #64748B;
  --cp-shadow: 0 24px 60px -24px rgba(0, 0, 0, 0.45);
  --cp-shadow-soft: 0 18px 40px -24px rgba(0, 0, 0, 0.35);
  --cp-serif: 'Lora', 'Liberation Serif', Georgia, serif;
  --cp-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --cp-mono: 'JetBrains Mono', 'Liberation Mono', ui-monospace, monospace;
}

html.light {
  --cp-bg: #f4ecea;
  --cp-panel: #fff5f3;
  --cp-panel-2: #ffe4df;
  --cp-border: rgba(26, 26, 46, 0.08);
  --cp-border-strong: rgba(26, 26, 46, 0.14);
  --cp-accent: #b94a4a;
  --cp-accent-deep: #67000E;
  --cp-text: #1A1A2E;
  --cp-text-soft: #334155;
  --cp-text-muted: #475569;
  --cp-text-dim: #64748B;
  --cp-shadow: 0 20px 40px -28px rgba(0, 0, 0, 0.18);
  --cp-shadow-soft: 0 14px 28px -24px rgba(0, 0, 0, 0.12);
}

body.course-ui {
  background: var(--cp-bg);
  color: var(--cp-text);
  font-family: var(--cp-sans);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.course-page {
  max-width: 1120px;
  margin: 0 auto;
  padding: calc(env(safe-area-inset-top, 0px) + 76px) 32px calc(env(safe-area-inset-bottom, 0px) + 72px);
}

.course-back {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: fit-content;
  margin-bottom: 8px;
  padding: 11px 16px;
  border-radius: 999px;
  border: 1px solid var(--cp-border-strong);
  background: rgba(255, 255, 255, 0.03);
  color: var(--cp-text-muted);
  font-family: var(--cp-sans);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  text-decoration: none;
  transition: transform .22s ease, border-color .22s ease, color .22s ease, background .22s ease;
}

html.light .course-back {
  background: rgba(255, 255, 255, 0.62);
}

.course-back:hover {
  transform: translateY(-2px);
  border-color: rgba(255, 99, 99, 0.34);
  color: var(--cp-accent);
  background: rgba(255, 99, 99, 0.08);
}

.page-stack {
  display: flex;
  flex-direction: column;
  gap: 28px;
}

.hero-card,
.section-card {
  background: var(--cp-panel);
  border: 1px solid var(--cp-border);
  border-radius: 28px;
  box-shadow: var(--cp-shadow-soft);
}

.hero-card {
  padding: 36px;
  position: relative;
  overflow: hidden;
}

.hero-card::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at top right, rgba(255, 99, 99, 0.14), transparent 32%),
    radial-gradient(circle at bottom left, rgba(255, 99, 99, 0.08), transparent 30%);
  pointer-events: none;
}

.hero-inner,
.section-inner {
  position: relative;
  z-index: 1;
}

.hero-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 20px;
  margin-bottom: 20px;
}

.hero-kicker,
.section-kicker {
  font-size: 12px;
  line-height: 16px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--cp-accent);
}

.hero-code {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 110px;
  padding: 10px 16px;
  border-radius: 999px;
  background: rgba(255, 99, 99, 0.12);
  color: var(--cp-accent);
  font-family: var(--cp-mono);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.hero-title {
  margin: 0;
  font-family: var(--cp-serif);
  font-size: clamp(34px, 5vw, 52px);
  line-height: 0.98;
  letter-spacing: -0.03em;
}

.hero-desc {
  max-width: 760px;
  margin: 16px 0 0;
  color: var(--cp-text-soft);
  font-size: 17px;
  line-height: 1.7;
}

.hero-prof-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 18px;
  padding: 8px 16px;
  border-radius: 9999px;
  font-family: var(--cp-sans);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.4px;
  text-transform: uppercase;
  background: rgba(255, 99, 99, 0.10);
  color: #FF6363;
  border: 1px solid rgba(255, 99, 99, 0.25);
  text-decoration: none;
  transition: background .15s, border-color .15s, transform .15s;
}
.hero-prof-link:hover {
  background: rgba(255, 99, 99, 0.18);
  border-color: #FF6363;
  transform: translateY(-1px);
}
html.light .hero-prof-link {
  background: rgba(185, 74, 74, 0.10);
  color: #b94a4a;
  border-color: rgba(185, 74, 74, 0.25);
}
html.light .hero-prof-link:hover {
  background: rgba(185, 74, 74, 0.18);
  border-color: #b94a4a;
}

.hero-stats {
  margin-top: 28px;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
}

.hero-stat {
  padding: 18px 20px;
  border-radius: 20px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--cp-border);
}

html.light .hero-stat {
  background: rgba(255, 255, 255, 0.55);
}

.hero-stat-value {
  display: block;
  font-family: var(--cp-serif);
  font-size: 28px;
  font-weight: 700;
  line-height: 1;
  color: var(--cp-text);
}

.hero-stat-label {
  display: block;
  margin-top: 10px;
  font-size: 12px;
  line-height: 16px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--cp-text-dim);
}

.hub-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 20px;
}

.hub-card {
  display: flex;
  flex-direction: column;
  min-height: 320px;
  border-radius: 28px;
  overflow: hidden;
  background: var(--cp-panel);
  border: 1px solid var(--cp-border);
  box-shadow: var(--cp-shadow-soft);
  color: inherit;
  text-decoration: none;
  transition: transform 0.22s ease, border-color 0.22s ease, box-shadow 0.22s ease;
}

.hub-card:hover {
  transform: translateY(-4px);
  border-color: rgba(255, 99, 99, 0.34);
  box-shadow: var(--cp-shadow);
}

.hub-media {
  position: relative;
  aspect-ratio: 1 / 0.9;
  overflow: hidden;
  background: #0d0d18;
}

.hub-media::after {
  content: "";
  position: absolute;
  inset: 0;
  background:
    linear-gradient(180deg, rgba(15, 13, 28, 0.08) 0%, rgba(15, 13, 28, 0.75) 100%),
    linear-gradient(180deg, rgba(15, 13, 28, 0.02) 10%, rgba(15, 13, 28, 0) 55%);
}

.hub-art {
  position: absolute;
  inset: 0;
  background-size: cover;
  background-position: center;
  transition: transform 0.3s ease;
}

.hub-card:hover .hub-art {
  transform: scale(1.04);
}

.hub-meta {
  position: absolute;
  left: 24px;
  right: 24px;
  bottom: 24px;
  z-index: 1;
}

.hub-meta-code {
  font-size: 11px;
  line-height: 15px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: #FF9A9A;
  font-weight: 700;
}

.hub-meta-title {
  margin-top: 6px;
  font-family: var(--cp-serif);
  font-size: 30px;
  line-height: 1;
  letter-spacing: -0.03em;
  color: #fff7f5;
}

.hub-body {
  display: flex;
  flex: 1;
  flex-direction: column;
  gap: 18px;
  padding: 22px 24px 24px;
}

.hub-body-title {
  margin: 0;
  font-family: var(--cp-serif);
  font-size: 26px;
  line-height: 1.08;
}

.hub-body-text {
  color: var(--cp-text-soft);
  font-size: 15px;
  line-height: 1.7;
}

.hub-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.hub-tag,
.chip {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 7px 10px;
  border-radius: 999px;
  border: 1px solid var(--cp-border);
  background: rgba(255, 255, 255, 0.03);
  color: var(--cp-text-muted);
  font-size: 12px;
  line-height: 16px;
}

html.light .hub-tag,
html.light .chip {
  background: rgba(255, 255, 255, 0.65);
}

.hub-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: auto;
  padding-top: 16px;
  border-top: 1px solid var(--cp-border);
  color: var(--cp-text-dim);
  font-size: 13px;
  line-height: 18px;
}

.hub-arrow {
  color: var(--cp-accent);
  font-family: var(--cp-mono);
  font-weight: 700;
}

.section-card {
  padding: 30px;
}

.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  margin-bottom: 24px;
}

.section-title {
  margin: 0;
  font-family: var(--cp-serif);
  font-size: 34px;
  line-height: 1.05;
  letter-spacing: -0.03em;
}

.section-subtitle {
  margin: 10px 0 0;
  color: var(--cp-text-soft);
  font-size: 15px;
  line-height: 1.7;
}

.topic-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.topic-card {
  padding: 22px;
  border-radius: 22px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--cp-border);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.02);
}

html.light .topic-card {
  background: rgba(255, 255, 255, 0.55);
}

.topic-row {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 14px;
}

.topic-code {
  font-family: var(--cp-mono);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--cp-text-dim);
}

.topic-status {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 10px;
  border-radius: 999px;
  font-size: 12px;
  line-height: 16px;
  border: 1px solid var(--cp-border);
}

.topic-status.active {
  color: var(--cp-accent);
  background: rgba(255, 99, 99, 0.12);
}

.topic-status.pending {
  color: #d38a00;
  background: rgba(251, 191, 36, 0.16);
}

.topic-status.upcoming {
  color: var(--cp-text-dim);
  background: rgba(255, 255, 255, 0.02);
}

.topic-title {
  margin: 0;
  font-family: var(--cp-serif);
  font-size: 24px;
  line-height: 1.1;
}

.topic-desc {
  margin: 10px 0 16px;
  color: var(--cp-text-soft);
  font-size: 14px;
  line-height: 1.7;
}

.topic-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.filter-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 22px;
}

.filter-btn {
  appearance: none;
  border: 1px solid var(--cp-border);
  background: transparent;
  color: var(--cp-text-muted);
  border-radius: 999px;
  padding: 9px 14px;
  font-family: var(--cp-sans);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  cursor: pointer;
  transition: border-color 0.2s ease, color 0.2s ease, background 0.2s ease;
}

.filter-btn.active,
.filter-btn:hover {
  border-color: rgba(255, 99, 99, 0.34);
  color: var(--cp-accent);
  background: rgba(255, 99, 99, 0.08);
}

.file-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.file-entry {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 18px;
  padding: 22px;
  border-radius: 22px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--cp-border);
  align-items: center;
}

html.light .file-entry {
  background: rgba(255, 255, 255, 0.6);
}

.file-entry.hidden {
  display: none;
}

.file-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 10px;
}

.type-chip {
  display: inline-flex;
  align-items: center;
  padding: 5px 9px;
  border-radius: 999px;
  font-size: 11px;
  line-height: 15px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-weight: 700;
}

.type-chip.quiz {
  background: rgba(255, 99, 99, 0.12);
  color: var(--cp-accent);
}

.type-chip.exam {
  background: rgba(251, 191, 36, 0.18);
  color: #b27a00;
}

.type-chip.reference {
  background: rgba(148, 163, 184, 0.16);
  color: var(--cp-text-muted);
}

.type-chip.homework {
  background: rgba(74, 222, 128, 0.16);
  color: #16a34a;
}

.type-chip.classwork {
  background: rgba(96, 165, 250, 0.16);
  color: #2563eb;
}

.type-chip.lab {
  background: rgba(168, 85, 247, 0.16);
  color: #7c3aed;
}

.file-label {
  color: var(--cp-text-dim);
  font-size: 12px;
  line-height: 16px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.file-title {
  margin: 0;
  font-family: var(--cp-serif);
  font-size: 24px;
  line-height: 1.08;
}

.file-desc {
  margin: 10px 0 0;
  color: var(--cp-text-soft);
  font-size: 14px;
  line-height: 1.7;
}

.file-actions {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 10px;
}

.file-date {
  color: var(--cp-text-dim);
  font-size: 12px;
  line-height: 16px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.action-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 11px 16px;
  border-radius: 999px;
  border: 1px solid rgba(255, 99, 99, 0.24);
  background: rgba(255, 99, 99, 0.1);
  color: var(--cp-accent);
  font-family: var(--cp-sans);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  text-decoration: none;
  transition: filter 0.2s ease, transform 0.2s ease;
}

.action-btn:hover {
  filter: brightness(1.04);
  transform: translateY(-1px);
}

.external-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.external-card {
  display: flex;
  flex-direction: column;
  gap: 12px;
  padding: 22px;
  border-radius: 22px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--cp-border);
  color: inherit;
  text-decoration: none;
  transition: transform 0.2s ease, border-color 0.2s ease;
}

html.light .external-card {
  background: rgba(255, 255, 255, 0.6);
}

.external-card:hover {
  transform: translateY(-2px);
  border-color: rgba(255, 99, 99, 0.34);
}

.external-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.external-title {
  margin: 0;
  font-family: var(--cp-serif);
  font-size: 22px;
  line-height: 1.1;
}

.external-desc {
  color: var(--cp-text-soft);
  font-size: 14px;
  line-height: 1.7;
}

.page-footer {
  margin-top: 12px;
  color: var(--cp-text-dim);
  font-size: 13px;
  line-height: 18px;
  text-align: center;
}

.reveal {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity .6s ease, transform .6s ease;
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

@media (max-width: 980px) {
  .hub-grid,
  .topic-grid,
  .external-grid {
    grid-template-columns: 1fr;
  }

  .hero-stats {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 760px) {
  .course-page {
    padding: calc(env(safe-area-inset-top, 0px) + 72px) 16px calc(env(safe-area-inset-bottom, 0px) + 42px);
  }

  .hero-card,
  .section-card {
    border-radius: 24px;
  }

  .hero-card,
  .section-card {
    padding: 22px;
  }

  .hero-top,
  .section-header,
  .file-entry {
    grid-template-columns: 1fr;
  }

  .hero-top,
  .section-header {
    flex-direction: column;
    align-items: flex-start;
  }

  .hero-code {
    min-width: 0;
  }

  .hero-title {
    font-size: clamp(30px, 10vw, 42px);
  }

  .hero-desc,
  .section-subtitle,
  .hub-body-text,
  .topic-desc,
  .file-desc,
  .external-desc {
    font-size: 14px;
    line-height: 1.65;
  }

  .hero-stat {
    padding: 16px 16px 14px;
  }

  .hub-card {
    min-height: 0;
  }

  .hub-media {
    aspect-ratio: 1 / 0.82;
  }

  .hub-meta {
    left: 18px;
    right: 18px;
    bottom: 18px;
  }

  .hub-meta-title {
    font-size: 24px;
  }

  .hub-body {
    padding: 18px 18px 20px;
    gap: 14px;
  }

  .hub-body-title,
  .topic-title,
  .file-title,
  .external-title {
    font-size: 22px;
  }

  .topic-card,
  .file-entry,
  .external-card {
    padding: 18px;
    border-radius: 18px;
  }

  .filter-row {
    gap: 8px;
    margin-bottom: 18px;
  }

  .filter-btn,
  .action-btn {
    min-height: 42px;
  }

  .file-entry {
    grid-template-columns: 1fr;
  }

  .file-actions {
    align-items: flex-start;
    width: 100%;
  }

  .action-btn {
    width: 100%;
  }
}

@media (max-width: 480px) {
  .hero-stats {
    gap: 10px;
  }

  .hero-stat-value {
    font-size: 24px;
  }

  .section-title {
    font-size: 28px;
  }

  .hub-tag,
  .chip,
  .topic-status,
  .type-chip {
    font-size: 11px;
  }

  .hub-footer,
  .file-date,
  .file-label,
  .hero-kicker,
  .section-kicker {
    font-size: 11px;
  }
}