:root {
  --bg: #FDFCFA;
  --bg-alt: #F6F3EB;
  --surface: #FFFFFF;
  --ink: #1A1A1A;
  --ink-2: #5A5A5A;
  --ink-3: #999999;
  --brand: #D9251C;
  --brand-soft: #FDF0EE;
  --line: #E8E4DF;
  --radius: 16px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font);
  background-color: var(--bg);
  color: var(--ink);
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}
img { display: block; max-width: 100%; }
a { text-decoration: none; color: inherit; }
button { font-family: inherit; cursor: pointer; border: none; background: none; }

/* 00 服务条 */
.top-bar {
  background-color: var(--ink);
  color: rgba(255, 255, 255, 0.84);
  font-size: 12.5px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0 16px;
  text-align: center;
}
.top-bar-badge {
  display: inline-block;
  font-size: 11px;
  line-height: 1;
  padding: 3px 5px;
  border: 1px solid rgba(255, 255, 255, 0.5);
  border-radius: 4px;
  margin-right: 8px;
  vertical-align: middle;
}

/* 01 导航 */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: rgba(253, 252, 250, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
}
.nav-container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 18px;
  font-weight: 700;
}
.brand img { height: 32px; width: auto; }
.nav-links {
  display: flex;
  gap: 24px;
}
.nav-links a {
  font-size: 14px;
  color: var(--ink-2);
  font-weight: 500;
  transition: color 0.2s;
}
.nav-links a:hover { color: var(--brand); }
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0 20px;
  height: 38px;
  border-radius: 999px;
  font-size: 14px;
  font-weight: 600;
  transition: all 0.2s;
}
.btn-primary {
  background-color: var(--ink);
  color: #fff;
}
.btn-primary:hover { background-color: #333; }
.btn-brand {
  background-color: var(--brand);
  color: #fff;
}
.btn-brand:hover { opacity: 0.9; }
.btn-outline {
  border: 1px solid var(--line);
  background-color: transparent;
  color: var(--ink);
}
.btn-outline:hover { border-color: var(--brand); color: var(--brand); }
.mobile-menu-btn { display: none; font-size: 24px; line-height: 1; color: var(--ink); }

/* 通用区块 */
.section {
  padding: 88px 0;
}
.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
}
.section-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  margin-bottom: 32px;
}
.section-title {
  font-size: 28px;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 8px;
}
.section-desc {
  font-size: 15px;
  color: var(--ink-2);
}

/* 02 首屏 */
.hero {
  display: flex;
  align-items: center;
  gap: 48px;
  padding-top: 64px;
  padding-bottom: 88px;
}
.hero-left {
  flex: 1.05;
}
.hero-right {
  flex: 1;
}
.hero-tag {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--brand);
  font-weight: 600;
  margin-bottom: 16px;
  display: block;
}
.hero-title {
  font-size: clamp(36px, 5vw, 58px);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin-bottom: 20px;
}
.hero-slogan {
  font-size: 20px;
  font-weight: 500;
  font-style: italic;
  color: var(--ink-2);
  margin-bottom: 16px;
}
.hero-desc {
  font-size: 15px;
  line-height: 1.85;
  color: var(--ink-2);
  margin-bottom: 32px;
}
.hero-actions {
  display: flex;
  gap: 16px;
  margin-bottom: 32px;
}
.hero-pills {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  max-width: 320px;
}
.pill {
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 6px 12px;
  font-size: 13px;
  color: var(--ink-2);
  text-align: center;
}
.stack {
  position: relative;
  width: 100%;
  aspect-ratio: 3 / 4;
}
.stack-main {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 64%;
  z-index: 2;
  border-radius: 12px;
  border: 1px solid rgba(255, 255, 255, 0.4);
  box-shadow: 0 20px 40px rgba(0,0,0,0.15);
  overflow: hidden;
  aspect-ratio: 3 / 4;
}
.stack-sub-a {
  position: absolute;
  top: -5%;
  left: 0;
  width: 32%;
  transform: rotate(-3deg);
  z-index: 1;
  border-radius: 10px;
  border: 1px solid rgba(255, 255, 255, 0.4);
  box-shadow: 0 10px 20px rgba(0,0,0,0.1);
  overflow: hidden;
  aspect-ratio: 3 / 4;
}
.stack-sub-b {
  position: absolute;
  bottom: -5%;
  right: 0;
  width: 32%;
  transform: rotate(3deg);
  z-index: 3;
  border-radius: 10px;
  border: 1px solid rgba(255, 255, 255, 0.4);
  box-shadow: 0 15px 30px rgba(0,0,0,0.12);
  overflow: hidden;
  aspect-ratio: 3 / 4;
}
.stack img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: 50% 22%;
}
.img-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, transparent 42%, rgba(0,0,0,0.5));
}

/* 03 双引擎 */
.engine-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  border: 1px dashed var(--line);
  border-radius: 20px;
  overflow: hidden;
  background-color: var(--bg-alt);
}
.engine-card {
  padding: 32px;
}
.engine-card:first-child {
  border-right: 1px dashed var(--line);
}
.engine-slogan {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 24px;
  color: var(--ink);
}
.engine-feature {
  margin-bottom: 20px;
}
.engine-feature:last-child { margin-bottom: 0; }
.engine-label {
  display: inline-block;
  font-size: 12px;
  color: var(--brand);
  font-weight: 600;
  margin-bottom: 4px;
}
.engine-text {
  font-size: 14px;
  color: var(--ink-2);
}

/* 04 内容线入口 */
.entry-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}
.entry-card {
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px;
  display: flex;
  flex-direction: column;
  transition: all 0.2s;
}
.entry-card:hover {
  transform: translateY(-2px);
  border-color: var(--brand);
}
.entry-icon {
  font-size: 24px;
  margin-bottom: 16px;
  color: var(--ink);
}
.entry-name {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 8px;
}
.entry-audience {
  font-size: 13px;
  color: var(--ink-2);
  flex: 1;
  margin-bottom: 24px;
}
.entry-link {
  font-size: 14px;
  font-weight: 600;
  color: var(--brand);
}

/* 05 题材频道墙 */
.genre-wall {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  border: 1px solid var(--line);
  background-color: var(--surface);
}
.genre-item {
  padding: 22px;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  position: relative;
  transition: background-color 0.2s;
  cursor: pointer;
}
.genre-item:nth-child(4n) { border-right: none; }
.genre-item:nth-child(n+5) { border-bottom: none; }
.genre-item:hover { background-color: var(--brand-soft); }
.genre-name {
  font-size: 15px;
  font-weight: 600;
}
.genre-arrow {
  font-size: 14px;
  color: var(--ink-3);
}

/* 06 排名轨道 */
.rank-track {
  display: flex;
  gap: 20px;
  overflow-x: auto;
  padding-bottom: 12px;
  scroll-snap-type: x mandatory;
}
.rank-item {
  flex: 0 0 calc(20% - 16px);
  scroll-snap-align: start;
}
.rank-num {
  font-size: 40px;
  font-weight: 800;
  color: var(--brand);
  opacity: 0.9;
  font-variant-numeric: tabular-nums;
  line-height: 1;
  margin-bottom: 8px;
}
.rank-cover {
  aspect-ratio: 3 / 4;
  border-radius: 10px;
  overflow: hidden;
  margin-bottom: 12px;
  position: relative;
}
.rank-cover img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: 50% 22%;
}
.rank-title {
  font-size: 13.5px;
  font-weight: 600;
  line-height: 1.4;
  margin-bottom: 4px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.rank-episodes {
  font-size: 12px;
  color: var(--ink-2);
}

/* 07 专题片单 */
.topic-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}
.topic-card {
  display: block;
  transition: transform 0.2s;
}
.topic-card:hover {
  transform: translateY(-2px);
}
.topic-cover {
  aspect-ratio: 3 / 4;
  border-radius: var(--radius);
  overflow: hidden;
  margin-bottom: 16px;
  position: relative;
}
.topic-cover img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: 50% 22%;
}
.topic-theme {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--brand);
  font-weight: 600;
  margin-bottom: 4px;
}
.topic-name {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 4px;
}
.topic-desc {
  font-size: 12.5px;
  color: var(--ink-2);
}

/* 08 安装区 */
.install-section {
  background-color: var(--bg-alt);
  border-radius: 24px;
  padding: 56px 24px;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
}
.install-title {
  font-size: 28px;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 16px;
}
.install-desc {
  font-size: 15px;
  color: var(--ink-2);
  margin-bottom: 40px;
  max-width: 400px;
}
.install-actions {
  display: flex;
  align-items: center;
  gap: 24px;
  margin-bottom: 24px;
}
.btn-large {
  height: 48px;
  padding: 0 32px;
  font-size: 16px;
  background-color: var(--surface);
  color: var(--ink);
  border: 1px solid var(--line);
  box-shadow: 0 4px 12px rgba(0,0,0,0.05);
}
.btn-large:hover {
  border-color: var(--brand);
  color: var(--brand);
}
.qr-box {
  width: 120px;
  height: 120px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  color: var(--ink-3);
  position: relative;
}
.qr-box::after {
  content: '';
  position: absolute;
  inset: 12px;
  border: 1px dashed var(--line);
}
.install-version {
  font-size: 12px;
  color: var(--ink-3);
}

/* 09 答疑区 */
.faq-list {
  border-top: 1px solid var(--line);
}
.faq-item {
  border-bottom: 1px solid var(--line);
}
.faq-summary {
  display: flex;
  align-items: flex-start;
  padding: 20px 0;
  cursor: pointer;
  list-style: none;
  position: relative;
}
.faq-summary::-webkit-details-marker { display: none; }
.faq-num {
  font-size: 12px;
  color: var(--ink-3);
  font-variant-numeric: tabular-nums;
  width: 42px;
  flex-shrink: 0;
  margin-top: 2px;
}
.faq-question {
  font-size: 15px;
  font-weight: 600;
  flex: 1;
  padding-right: 32px;
}
.faq-icon {
  position: absolute;
  right: 0;
  top: 24px;
  width: 22px;
  height: 22px;
}
.faq-icon::before,
.faq-icon::after {
  content: '';
  position: absolute;
  background-color: var(--ink);
  transition: transform 0.3s, opacity 0.3s;
}
.faq-icon::before {
  top: 50%; left: 0; width: 100%; height: 1.5px; transform: translateY(-50%);
}
.faq-icon::after {
  left: 50%; top: 0; width: 1.5px; height: 100%; transform: translateX(-50%);
}
details[open] .faq-icon::after { transform: translateX(-50%) rotate(90deg); opacity: 0; }
.faq-answer {
  font-size: 13.5px;
  line-height: 1.85;
  color: var(--ink-2);
  padding: 0 0 20px 42px;
}

/* 10 页脚 */
.footer {
  padding: 64px 0 48px;
  border-top: 1px solid var(--line);
  margin-bottom: 64px; /* 预留吸底条 */
}
.footer-top {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 32px;
}
.footer-brand {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 8px;
}
.footer-slogan {
  font-size: 14px;
  color: var(--ink-2);
}
.back-to-top {
  font-size: 14px;
  color: var(--ink-2);
  font-weight: 500;
}
.footer-links {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 32px;
}
.footer-link-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  font-size: 14px;
  color: var(--ink-2);
}
.footer-link-row a:hover { color: var(--brand); }
.footer-link-row span.divider {
  margin: 0 8px;
  color: var(--ink-3);
}
.footer-bottom {
  font-size: 12px;
  color: var(--ink-3);
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  align-items: center;
}

/* 吸底条 */
.sticky-bar {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background-color: var(--surface);
  border-top: 1px solid var(--line);
  padding: 12px 16px calc(12px + env(safe-area-inset-bottom));
  z-index: 100;
  justify-content: space-between;
  align-items: center;
  box-shadow: 0 -4px 12px rgba(0,0,0,0.05);
}
.sticky-bar-text {
  font-size: 13px;
  font-weight: 500;
}
.sticky-bar-btn {
  height: 38px;
  padding: 0 20px;
}

/* 响应式 */
@media (max-width: 1024px) {
  .hero { flex-direction: column; gap: 48px; text-align: center; }
  .hero-left { order: 1; }
  .hero-right { order: 2; max-width: 400px; margin: 0 auto; width: 100%; }
  .hero-actions { justify-content: center; }
  .hero-pills { margin: 0 auto; }
  .engine-grid { grid-template-columns: 1fr; border-style: solid; border: 1px solid var(--line); background-color: transparent; gap: 20px; }
  .engine-card { background-color: var(--bg-alt); border-radius: 20px; }
  .engine-card:first-child { border-right: none; }
  .rank-item { flex: 0 0 calc(33.33% - 14px); }
  .topic-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
  .section { padding: 52px 0; }
  .hero { padding-top: 40px; padding-bottom: 52px; }
  .nav-links { display: none; }
  .mobile-menu-btn { display: block; }
  .hero-pills { grid-template-columns: 1fr 1fr; }
  .hero-pills .pill:last-child { grid-column: span 2; }
  .entry-grid { grid-template-columns: 1fr; }
  .genre-wall { grid-template-columns: repeat(2, 1fr); }
  .genre-item:nth-child(2n) { border-right: none; }
  .genre-item:nth-child(n+7) { border-bottom: none; }
  .genre-item:nth-child(5) { border-bottom: 1px solid var(--line); }
  .genre-item:nth-child(6) { border-bottom: 1px solid var(--line); }
  .rank-track { gap: 16px; }
  .rank-item { flex: 0 0 44vw; }
  .topic-grid { display: flex; overflow-x: auto; scroll-snap-type: x mandatory; padding-bottom: 12px; gap: 16px; }
  .topic-card { flex: 0 0 62vw; scroll-snap-align: start; }
  .install-actions { flex-direction: column; }
  .sticky-bar { display: flex; }
  .footer-top { flex-direction: column; gap: 24px; }
}