:root {
  --bg: #0a0c11;
  --bg-alt: #10141d;
  --panel: rgba(18, 21, 31, 0.92);
  --panel-strong: #161b26;
  --panel-soft: rgba(28, 33, 48, 0.9);
  --line: rgba(255, 255, 255, 0.08);
  --line-strong: rgba(104, 133, 255, 0.28);
  --text: #f4f7ff;
  --muted: #98a3bd;
  --accent: #5a8cff;
  --accent-strong: #7ca4ff;
  --accent-soft: rgba(90, 140, 255, 0.16);
  --green: #5ed09a;
  --shadow: 0 28px 60px rgba(0, 0, 0, 0.38);
  --radius-xl: 26px;
  --radius-lg: 20px;
  --radius-md: 16px;
  --font-sans: "Avenir Next", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-display: "Trebuchet MS", "Avenir Next", "PingFang SC", sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--text);
  background:
    radial-gradient(circle at top, rgba(71, 96, 198, 0.18), transparent 26%),
    radial-gradient(circle at 85% 12%, rgba(0, 211, 255, 0.1), transparent 22%),
    linear-gradient(180deg, #08090d 0%, #0d1118 100%);
  font-family: var(--font-sans);
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(255, 255, 255, 0.018) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.018) 1px, transparent 1px);
  background-size: 24px 24px;
  mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.8), transparent 92%);
}

a {
  color: inherit;
  text-decoration: none;
}

code {
  padding: 0.12rem 0.42rem;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.08);
  color: #d9e5ff;
  font-size: 0.92em;
}

img {
  max-width: 100%;
  display: block;
}

.site-shell {
  width: min(calc(100% - 32px), 1180px);
  margin: 0 auto 56px;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 40;
  backdrop-filter: blur(18px);
  background: rgba(8, 10, 15, 0.72);
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.topbar-inner {
  width: min(calc(100% - 32px), 1180px);
  margin: 0 auto;
  min-height: 72px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
}

.brand-mark {
  width: 42px;
  height: 42px;
  border-radius: 14px;
  display: grid;
  place-items: center;
  background: linear-gradient(135deg, rgba(90, 140, 255, 0.9), rgba(113, 230, 255, 0.8));
  color: #07101f;
  font-weight: 800;
}

.brand-text {
  display: grid;
  gap: 2px;
}

.brand-text strong,
.hero-panel h1,
.portal-card h3,
.section-heading h2,
.catalog-title,
.lesson-summary h1,
.source-card h3,
.info-panel h2 {
  font-family: var(--font-display);
}

.brand-text small {
  color: var(--muted);
  font-size: 0.78rem;
}

.topnav {
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

.topnav a {
  min-height: 38px;
  padding: 0 14px;
  border-radius: 999px;
  display: inline-flex;
  align-items: center;
  color: var(--muted);
  transition: background-color 180ms ease, color 180ms ease, transform 180ms ease;
}

.topnav a:hover,
.topnav a.is-active {
  color: var(--text);
  background: rgba(255, 255, 255, 0.06);
  transform: translateY(-1px);
}

.hero-panel,
.portal-section,
.portal-card,
.catalog-item,
.info-panel,
.stat-card,
.source-card,
.practice-card,
.lesson-hero {
  border: 1px solid var(--line);
  background: var(--panel);
  box-shadow: var(--shadow);
}

.hero-panel {
  margin-top: 28px;
  padding: 30px;
  border-radius: 30px;
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) 320px;
  gap: 24px;
  position: relative;
  overflow: hidden;
}

.hero-panel::after,
.lesson-hero::after {
  content: "";
  position: absolute;
  inset: auto -12% -42% auto;
  width: 280px;
  height: 280px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(90, 140, 255, 0.24), transparent 70%);
  pointer-events: none;
}

.hero-copy {
  position: relative;
  z-index: 1;
}

.hero-kicker,
.section-kicker {
  margin: 0 0 10px;
  font-size: 0.76rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: #7eb0ff;
}

.hero-panel h1,
.lesson-summary h1 {
  margin: 0;
  line-height: 1.02;
}

.hero-panel h1 {
  font-size: clamp(2.6rem, 6vw, 4.8rem);
  max-width: 720px;
}

.hero-lead,
.section-note,
.portal-card p,
.catalog-item p,
.source-card p,
.lesson-description,
.detail-list li,
.lesson-article p,
.practice-card p {
  color: var(--muted);
  line-height: 1.72;
}

.hero-lead,
.lesson-description {
  margin: 16px 0 0;
  max-width: 720px;
  font-size: 1.04rem;
}

.hero-actions,
.lesson-action-row,
.pager-row,
.tag-row,
.chip-row,
.lesson-meta-strip {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.hero-actions {
  margin-top: 26px;
}

.button {
  min-height: 44px;
  padding: 0 18px;
  border-radius: 12px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
  transition: transform 180ms ease, background-color 180ms ease, border-color 180ms ease;
}

.button:hover {
  transform: translateY(-2px);
}

.button.primary {
  color: #08111f;
  background: linear-gradient(135deg, #6aa2ff, #86c3ff);
}

.button.ghost {
  color: var(--text);
  border: 1px solid rgba(255, 255, 255, 0.12);
  background: rgba(255, 255, 255, 0.04);
}

.hero-preview,
.lesson-poster {
  min-height: 260px;
  border-radius: 24px;
  border: 1px solid rgba(255, 255, 255, 0.08);
  background:
    radial-gradient(circle at 24% 18%, rgba(126, 176, 255, 0.38), transparent 24%),
    linear-gradient(180deg, rgba(16, 21, 33, 0.95), rgba(11, 14, 22, 0.98));
  position: relative;
  overflow: hidden;
}

.preview-grid {
  position: absolute;
  inset: 18px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
}

.preview-grid span,
.lesson-poster-art::before,
.lesson-poster-art::after {
  border-radius: 18px;
  background: linear-gradient(180deg, rgba(90, 140, 255, 0.2), rgba(255, 255, 255, 0.03));
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.preview-grid span:nth-child(1) {
  grid-row: span 2;
}

.preview-grid span:nth-child(4) {
  grid-column: span 2;
}

.chip-row {
  margin: 18px 0 28px;
}

.chip,
.badge,
.tag {
  display: inline-flex;
  align-items: center;
  min-height: 34px;
  padding: 0 12px;
  border-radius: 999px;
  font-size: 0.9rem;
}

.chip {
  color: var(--muted);
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(255, 255, 255, 0.06);
}

.chip.is-selected,
.badge-accent {
  color: #dfe9ff;
  background: var(--accent-soft);
  border: 1px solid var(--line-strong);
}

.badge-soft,
.tag {
  color: #d0daf2;
  background: rgba(255, 255, 255, 0.06);
}

.portal-section {
  padding: 24px;
  border-radius: 28px;
  margin-bottom: 24px;
}

.section-heading {
  margin-bottom: 18px;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: end;
}

.section-heading.compact {
  margin-bottom: 14px;
}

.section-heading h2,
.info-panel h2 {
  margin: 0;
  font-size: clamp(1.5rem, 3vw, 2rem);
  line-height: 1.08;
}

.card-grid {
  display: grid;
  gap: 16px;
}

.home-project-grid {
  grid-template-columns: minmax(0, 1fr);
}

.units-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.source-grid,
.practice-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.portal-card,
.source-card,
.practice-card,
.info-panel,
.catalog-item {
  border-radius: 22px;
  transition: transform 180ms ease, border-color 180ms ease, background-color 180ms ease;
}

.portal-card:hover,
.source-card:hover,
.practice-card:hover,
.catalog-item:hover {
  transform: translateY(-3px);
  border-color: rgba(126, 176, 255, 0.26);
}

.featured-project {
  display: grid;
  grid-template-columns: 300px minmax(0, 1fr);
  gap: 22px;
  padding: 22px;
}

.card-cover {
  min-height: 240px;
  border-radius: 20px;
  border: 1px solid rgba(255, 255, 255, 0.06);
  position: relative;
  overflow: hidden;
}

.rag-cover {
  background:
    radial-gradient(circle at 18% 22%, rgba(106, 162, 255, 0.6), transparent 24%),
    radial-gradient(circle at 78% 72%, rgba(94, 208, 154, 0.2), transparent 24%),
    linear-gradient(160deg, #0b1120 0%, #16192a 60%, #0f1017 100%);
}

.cover-orbit {
  position: absolute;
  inset: 18px;
  border-radius: 50%;
  border: 1px solid rgba(126, 176, 255, 0.24);
}

.orbit-b {
  inset: 48px;
}

.cover-glow {
  position: absolute;
  inset: auto 18% 18% auto;
  width: 120px;
  height: 120px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(126, 176, 255, 0.32), transparent 70%);
}

.card-body {
  display: grid;
  align-content: start;
  gap: 14px;
}

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

.meta-text {
  color: var(--muted);
  font-size: 0.92rem;
}

.portal-card h3,
.source-card h3 {
  margin: 0;
  font-size: 1.7rem;
}

.card-link {
  color: #9fc0ff;
  font-weight: 600;
}

.back-link {
  display: inline-flex;
  min-height: 40px;
  align-items: center;
  padding: 0 14px;
  margin: 28px 0 16px;
  border-radius: 999px;
  color: var(--muted);
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(255, 255, 255, 0.06);
}

.project-hero {
  grid-template-columns: minmax(0, 1fr) 280px;
}

.project-stats {
  display: grid;
  gap: 14px;
}

.stat-card {
  padding: 20px;
  border-radius: 20px;
  background: var(--panel-soft);
}

.stat-card strong {
  display: block;
  font-size: 2.2rem;
  font-family: var(--font-display);
}

.stat-card span {
  color: var(--muted);
}

.unit-card {
  padding: 20px;
}

.unit-top {
  display: flex;
  gap: 14px;
  align-items: start;
  margin-bottom: 14px;
}

.unit-index,
.catalog-index {
  width: 52px;
  height: 52px;
  border-radius: 16px;
  display: grid;
  place-items: center;
  color: #dfe9ff;
  background: linear-gradient(135deg, rgba(90, 140, 255, 0.3), rgba(90, 140, 255, 0.08));
  border: 1px solid rgba(126, 176, 255, 0.24);
  flex: none;
  font-weight: 700;
}

.unit-card h3,
.catalog-title {
  margin: 0 0 6px;
  font-size: 1.12rem;
}

.catalog-list {
  display: grid;
  gap: 12px;
}

.catalog-item {
  padding: 18px 20px;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: center;
  background: var(--panel-strong);
}

.catalog-main {
  min-width: 0;
  display: flex;
  gap: 14px;
  align-items: start;
}

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

.catalog-copy p {
  margin: 0;
}

.catalog-meta {
  margin-top: 10px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.catalog-item.is-current {
  border-color: rgba(126, 176, 255, 0.34);
  background:
    linear-gradient(90deg, rgba(90, 140, 255, 0.14), transparent 34%),
    var(--panel-strong);
}

.catalog-action {
  color: #cfe0ff;
  white-space: nowrap;
  font-weight: 600;
}

.source-card,
.practice-card,
.info-panel {
  padding: 20px;
  background: var(--panel-strong);
}

.source-card-header {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: start;
  margin-bottom: 12px;
}

.text-link {
  color: #9fc0ff;
  font-weight: 600;
}

.lesson-shell {
  padding-bottom: 28px;
}

.reader-shell {
  max-width: 980px;
  padding-bottom: 28px;
}

.reader-back-row {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.lesson-hero {
  padding: 24px;
  border-radius: 28px;
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  gap: 24px;
  position: relative;
  overflow: hidden;
  margin-bottom: 24px;
}

.reader-header {
  padding: 28px;
  border-radius: 28px;
  border: 1px solid var(--line);
  background:
    radial-gradient(circle at top right, rgba(90, 140, 255, 0.14), transparent 24%),
    var(--panel);
  box-shadow: var(--shadow);
  margin-bottom: 24px;
}

.reader-header-copy {
  max-width: 780px;
}

.reader-content-layout {
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
  gap: 18px;
  align-items: start;
  margin-bottom: 24px;
}

.reader-outline-card {
  position: sticky;
  top: 92px;
  padding: 20px;
  border-radius: 24px;
  border: 1px solid var(--line);
  background: var(--panel);
  box-shadow: var(--shadow);
}

.reader-section-list {
  display: grid;
  gap: 10px;
}

.reader-section-item {
  width: 100%;
  padding: 14px;
  border: 1px solid rgba(255, 255, 255, 0.06);
  border-radius: 16px;
  background: rgba(255, 255, 255, 0.03);
  color: var(--text);
  display: grid;
  grid-template-columns: 44px minmax(0, 1fr);
  gap: 12px;
  text-align: left;
  cursor: pointer;
  transition: transform 180ms ease, border-color 180ms ease, background-color 180ms ease;
}

.reader-section-item:hover,
.reader-section-item.is-active {
  transform: translateY(-1px);
  border-color: rgba(126, 176, 255, 0.3);
  background: rgba(90, 140, 255, 0.1);
}

.reader-section-item.is-active {
  box-shadow: inset 0 0 0 1px rgba(126, 176, 255, 0.16);
}

.reader-section-index {
  width: 44px;
  height: 44px;
  border-radius: 14px;
  display: grid;
  place-items: center;
  font-weight: 700;
  color: #dfe9ff;
  background: linear-gradient(135deg, rgba(90, 140, 255, 0.26), rgba(90, 140, 255, 0.08));
}

.reader-section-name {
  align-self: center;
  line-height: 1.5;
}

.reader-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 18px;
}

.reader-article-panel {
  padding-bottom: 32px;
}

.lesson-poster {
  min-height: 280px;
}

.lesson-poster-art {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 18% 18%, rgba(126, 176, 255, 0.38), transparent 22%),
    radial-gradient(circle at 78% 24%, rgba(255, 255, 255, 0.14), transparent 12%),
    radial-gradient(circle at 68% 72%, rgba(94, 208, 154, 0.16), transparent 22%),
    linear-gradient(160deg, #0d1121 0%, #171c2d 70%, #0c0e17 100%);
}

.lesson-poster-art::before,
.lesson-poster-art::after {
  content: "";
  position: absolute;
}

.lesson-poster-art::before {
  inset: 20px;
  border-radius: 22px;
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.08);
}

.lesson-poster-art::after {
  inset: auto 28px 24px auto;
  width: 116px;
  height: 116px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(126, 176, 255, 0.26), transparent 68%);
}

.lesson-summary {
  position: relative;
  z-index: 1;
  display: grid;
  align-content: center;
  gap: 16px;
}

.lesson-summary h1 {
  font-size: clamp(2rem, 4vw, 3rem);
}

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

.detail-list,
.lesson-article ul {
  margin: 0;
  padding-left: 18px;
}

.detail-list li + li,
.lesson-article li + li {
  margin-top: 10px;
}

.lesson-catalog .catalog-item {
  align-items: start;
}

.lesson-article {
  max-width: 860px;
}

.lesson-article > *:first-child {
  margin-top: 0;
}

.lesson-article h1,
.lesson-article h2,
.lesson-article h3 {
  font-family: var(--font-display);
  line-height: 1.18;
}

.lesson-article h2 {
  margin-top: 30px;
  font-size: 1.8rem;
}

.lesson-article h3 {
  margin-top: 24px;
  font-size: 1.28rem;
}

.lesson-article p {
  margin: 14px 0 0;
}

.lesson-article pre {
  overflow: auto;
  padding: 16px;
  border-radius: 16px;
  background: #0d1017;
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.lesson-article blockquote {
  margin: 18px 0 0;
  padding: 14px 16px;
  border-left: 3px solid rgba(126, 176, 255, 0.48);
  background: rgba(255, 255, 255, 0.03);
  color: #c8d5f0;
}

.lesson-article figure {
  margin: 22px 0 0;
  display: grid;
  gap: 10px;
}

.lesson-article figcaption {
  color: var(--muted);
  font-size: 0.92rem;
}

.pager-row {
  margin-top: 18px;
  justify-content: space-between;
}

@media (max-width: 980px) {
  .hero-panel,
  .project-hero,
  .featured-project,
  .lesson-hero,
  .reader-header,
  .reader-content-layout,
  .summary-columns {
    grid-template-columns: 1fr;
  }

  .units-grid,
  .source-grid,
  .practice-grid {
    grid-template-columns: 1fr;
  }

  .section-heading {
    align-items: start;
    flex-direction: column;
  }
}

@media (max-width: 720px) {
  .topbar-inner,
  .site-shell {
    width: min(calc(100% - 24px), 1180px);
  }

  .topbar-inner {
    min-height: 64px;
  }

  .brand-text small,
  .topnav {
    display: none;
  }

  .hero-panel,
  .portal-section,
  .lesson-hero,
  .reader-header {
    padding: 20px;
    border-radius: 22px;
  }

  .hero-panel h1 {
    font-size: 2.4rem;
  }

  .catalog-item,
  .catalog-main {
    flex-direction: column;
    align-items: start;
  }

  .catalog-action {
    padding-left: 66px;
  }
}