:root {
    --bg: #F9F8F5;
    --bg-alt: #F0EFEA;
    --surface: #FFFFFF;
    --ink: #1C1B1A;
    --ink-2: #595754;
    --ink-3: #9A9793;
    --brand: #D62F38;
    --brand-soft: #FDF2F2;
    --line: #E3E1DC;
    
    --font-sys: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --radius-card: 16px;
    --radius-lrg: 20px;
    --radius-xl: 24px;
  }

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

  html {
    scroll-behavior: smooth;
  }

  body {
    font-family: var(--font-sys);
    background-color: var(--bg);
    color: var(--ink);
    line-height: 1.8;
    font-size: 15px;
    -webkit-font-smoothing: antialiased;
  }

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

  ul {
    list-style: none;
  }

  button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    background: none;
  }

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

  .container {
    max-width: 1080px;
    margin: 0 auto;
    padding: 0 24px;
  }

  /* Typography */
  h1, h2, h3, h4 {
    font-weight: 700;
    line-height: 1.3;
  }
  
  .title-800 { font-weight: 800; }

  /* Common Section Spacing */
  section {
    padding: 88px 0;
  }

  @media (max-width: 768px) {
    section {
      padding: 52px 0;
    }
  }

  /* Buttons */
  .btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0 24px;
    height: 44px;
    border-radius: 999px;
    font-size: 14px;
    font-weight: 600;
    transition: all 0.2s ease;
  }

  .btn-primary {
    background-color: var(--brand);
    color: #FFF;
  }

  .btn-primary:hover {
    opacity: 0.9;
    transform: translateY(-2px);
  }

  .btn-outline {
    border: 1px solid var(--line);
    background-color: transparent;
    color: var(--ink);
  }

  .btn-outline:hover {
    border-color: var(--brand);
    color: var(--brand);
  }

  /* 00 · 服务条 */
  .notice-bar {
    background-color: var(--ink);
    color: rgba(255, 255, 255, 0.84);
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 12.5px;
    padding: 0 16px;
    text-align: center;
  }

  .badge-18 {
    display: inline-block;
    font-size: 11px;
    border: 1px solid rgba(255, 255, 255, 0.4);
    border-radius: 4px;
    padding: 0 4px;
    margin-right: 8px;
    line-height: 1.4;
    vertical-align: middle;
  }

  /* 01 · 导航 */
  .header-nav {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: rgba(249, 248, 245, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--line);
  }

  .nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
  }

  .brand-logo {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 18px;
    font-weight: 700;
    letter-spacing: -0.02em;
  }

  .brand-logo img {
    height: 32px;
    width: auto;
  }

  .nav-links {
    display: flex;
    gap: 32px;
    font-size: 14px;
    font-weight: 500;
  }

  .nav-links a:hover {
    color: var(--brand);
  }

  .nav-actions {
    display: flex;
    align-items: center;
    gap: 16px;
  }

  .mobile-menu-btn {
    display: none;
  }

  /* 02 · 首屏 */
  .hero {
    display: flex;
    align-items: center;
    gap: 48px;
    padding-top: 64px;
  }

  .hero-left {
    flex: 1.05;
  }

  .hero-right {
    flex: 1;
    position: relative;
  }

  .hero-tag {
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 0.2em;
    color: var(--ink-2);
    margin-bottom: 16px;
    display: block;
  }

  .hero h1 {
    font-size: clamp(36px, 4vw, 58px);
    font-weight: 800;
    letter-spacing: -0.02em;
    margin-bottom: 24px;
    color: var(--ink);
  }

  .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;
    max-width: 85%;
  }

  .hero-btns {
    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: 8px 16px;
    font-size: 12.5px;
    text-align: center;
    color: var(--ink-2);
  }

  .hero-stack {
    position: relative;
    width: 100%;
    aspect-ratio: 4/5;
    margin: 0 auto;
  }

  .hero-img {
    position: absolute;
    border-radius: 12px;
    border: 1px solid #FFF;
    box-shadow: 0 12px 32px rgba(0,0,0,0.1);
    object-fit: cover;
    object-position: 50% 22%;
  }
  
  .hero-img::after {
    content: '';
    display: block;
    position: absolute;
    inset: 0;
    background: linear-gradient(180deg, transparent 42%, rgba(0,0,0,.5));
    border-radius: inherit;
  }

  .hero-img-main {
    width: 64%;
    aspect-ratio: 3/4;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    z-index: 2;
  }

  .hero-img-a {
    width: 32%;
    aspect-ratio: 3/4;
    top: -5%;
    left: 0;
    transform: rotate(-3deg);
    z-index: 1;
  }

  .hero-img-b {
    width: 32%;
    aspect-ratio: 3/4;
    bottom: -5%;
    right: 0;
    transform: rotate(3deg);
    z-index: 3;
  }

  /* 03 · 双引擎对照 */
  .engine-section {
    display: flex;
    position: relative;
  }

  .engine-card {
    flex: 1;
    background-color: var(--bg-alt);
    border-radius: var(--radius-lrg);
    padding: 32px;
  }

  .engine-card:first-child {
    margin-right: 32px;
  }

  .engine-card:last-child {
    margin-left: 32px;
  }

  .engine-divider {
    position: absolute;
    top: 10%;
    bottom: 10%;
    left: 50%;
    border-left: 1px dashed var(--ink-3);
    opacity: 0.5;
    transform: translateX(-50%);
  }

  .engine-card h3 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 24px;
  }

  .engine-feature {
    margin-bottom: 16px;
  }

  .engine-tag {
    display: inline-block;
    font-size: 12px;
    font-weight: 600;
    color: var(--brand);
    margin-bottom: 4px;
  }

  .engine-feature p {
    font-size: 13px;
  }

  /* 04 · 内容线入口 */
  .entry-cards {
    display: flex;
    gap: 20px;
  }

  .entry-card {
    flex: 1;
    background-color: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius-card);
    padding: 32px 24px;
    display: flex;
    flex-direction: column;
    transition: all 0.2s ease;
  }

  .entry-card:hover {
    border-color: var(--brand);
    transform: translateY(-2px);
  }

  .entry-icon {
    width: 24px;
    height: 24px;
    margin-bottom: 16px;
  }

  .entry-card h3 {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 8px;
  }

  .entry-card p {
    font-size: 13px;
    color: var(--ink-2);
    margin-bottom: 24px;
    flex: 1;
  }

  .entry-link {
    font-size: 13px;
    font-weight: 600;
    color: var(--brand);
    display: inline-flex;
    align-items: center;
    gap: 4px;
  }

  /* 05 · 题材频道墙 */
  .genre-wall {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    border: 1px solid var(--line);
    background-color: var(--line);
    gap: 1px;
  }

  .genre-item {
    background-color: var(--surface);
    padding: 22px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: background-color 0.2s ease;
    cursor: pointer;
  }

  .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-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    margin-bottom: 24px;
  }

  .rank-header h2 {
    font-size: 24px;
    font-weight: 700;
  }

  .rank-header a {
    font-size: 13px;
    color: var(--ink-2);
    font-weight: 500;
  }

  .rank-track {
    display: flex;
    gap: 20px;
    overflow-x: auto;
    padding-bottom: 12px;
    scroll-snap-type: x mandatory;
  }

  .rank-track::-webkit-scrollbar {
    display: none;
  }

  .rank-item {
    flex: 1;
    min-width: 0;
    scroll-snap-align: start;
    display: flex;
    gap: 12px;
  }

  .rank-num {
    font-size: 40px;
    font-weight: 800;
    color: var(--brand);
    line-height: 1;
    font-variant-numeric: tabular-nums;
    opacity: 0.9;
  }

  .rank-content {
    flex: 1;
  }

  .rank-cover {
    width: 100%;
    aspect-ratio: 3/4;
    border-radius: 10px;
    object-fit: cover;
    object-position: 50% 22%;
    margin-bottom: 12px;
  }

  .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-meta {
    font-size: 12px;
    color: var(--ink-2);
  }

  /* 07 · 专题片单 */
  .topic-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
  }

  .topic-card {
    display: block;
  }

  .topic-cover {
    width: 100%;
    aspect-ratio: 3/4;
    border-radius: var(--radius-card);
    object-fit: cover;
    object-position: 50% 22%;
    margin-bottom: 16px;
    transition: transform 0.2s ease;
  }

  .topic-card:hover .topic-cover {
    transform: translateY(-2px);
  }

  .topic-tag {
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 0.14em;
    color: var(--brand);
    margin-bottom: 8px;
    display: block;
  }

  .topic-name {
    font-size: 20px;
    font-weight: 700;
    margin-bottom: 8px;
  }

  .topic-desc {
    font-size: 12.5px;
    color: var(--ink-2);
  }

  /* 08 · 安装区 */
  .install-section {
    background-color: var(--bg-alt);
    border-radius: var(--radius-xl);
    padding: 56px;
    text-align: center;
  }

  .install-section h2 {
    font-size: 28px;
    font-weight: 700;
    margin-bottom: 16px;
    line-height: 1.4;
  }

  .install-desc {
    font-size: 15px;
    color: var(--ink-2);
    margin-bottom: 32px;
  }

  .install-action {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 24px;
    margin-bottom: 24px;
  }

  .install-btn {
    height: 48px;
    background-color: #FFF;
    color: var(--ink);
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
  }

  .install-btn:hover {
    box-shadow: 0 6px 16px rgba(0,0,0,0.08);
    transform: translateY(-2px);
  }

  .qr-code-box {
    width: 120px;
    height: 120px;
    background-color: #FFF;
    border: 1px solid var(--line);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 8px;
  }
  
  .qr-code-box img {
    width: 100%;
    height: 100%;
    object-fit: contain;
  }

  .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-item summary {
    display: flex;
    align-items: center;
    padding: 24px 0;
    cursor: pointer;
    list-style: none;
  }

  .faq-item 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;
  }

  .faq-q {
    font-size: 15px;
    font-weight: 600;
    flex: 1;
  }

  .faq-icon {
    width: 22px;
    height: 22px;
    position: relative;
    flex-shrink: 0;
  }

  .faq-icon::before,
  .faq-icon::after {
    content: '';
    position: absolute;
    background-color: var(--ink);
    transition: all 0.2s ease;
  }

  .faq-icon::before {
    width: 14px;
    height: 2px;
    top: 10px;
    left: 4px;
  }

  .faq-icon::after {
    width: 2px;
    height: 14px;
    top: 4px;
    left: 10px;
  }

  details[open] .faq-icon::after {
    transform: rotate(90deg);
    opacity: 0;
  }

  .faq-a {
    font-size: 13.5px;
    line-height: 1.85;
    color: var(--ink-2);
    padding: 0 0 24px 42px;
  }

  /* 10 · 页脚 */
  .footer {
    padding: 64px 0 32px;
    border-top: 1px solid var(--line);
    background-color: var(--bg);
  }

  .footer-top {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 48px;
  }

  .footer-brand {
    display: flex;
    flex-direction: column;
    gap: 12px;
  }
  
  .footer-brand .name {
    font-size: 18px;
    font-weight: 700;
  }

  .footer-slogan {
    font-size: 14px;
    color: var(--ink-2);
  }

  .back-to-top {
    font-size: 14px;
    color: var(--ink-2);
    font-weight: 500;
  }

  .footer-links {
    margin-bottom: 24px;
  }

  .footer-links-line {
    font-size: 14px;
    color: var(--ink-2);
    margin-bottom: 8px;
  }

  .footer-links-line a:hover {
    color: var(--ink);
  }

  .footer-bottom {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    align-items: center;
    font-size: 12px;
    color: var(--ink-3);
    padding-top: 24px;
    border-top: 1px solid var(--line);
  }

  .footer-meta {
    display: flex;
    align-items: center;
    gap: 16px;
  }

  /* Responsive */
  @media (max-width: 900px) {
    .hero {
      flex-direction: column;
      text-align: center;
      padding-top: 40px;
    }
    
    .hero-desc {
      margin: 0 auto 32px;
    }
    
    .hero-btns {
      justify-content: center;
    }
    
    .hero-pills {
      margin: 0 auto;
    }
    
    .hero-stack {
      aspect-ratio: 3/4;
      max-width: 400px;
    }

    .hero-img-a, .hero-img-b {
      display: none;
    }
    
    .hero-img-main {
      width: 100%;
      height: 100%;
      transform: none;
      top: 0;
      left: 0;
    }

    .engine-section {
      flex-direction: column;
    }

    .engine-card:first-child {
      margin-right: 0;
      margin-bottom: 24px;
    }

    .engine-card:last-child {
      margin-left: 0;
    }

    .engine-divider {
      display: none;
    }

    .entry-cards {
      flex-direction: column;
    }

    .genre-wall {
      grid-template-columns: repeat(2, 1fr);
    }

    .topic-grid {
      display: flex;
      overflow-x: auto;
      scroll-snap-type: x mandatory;
      gap: 16px;
      padding-bottom: 16px;
    }
    
    .topic-grid::-webkit-scrollbar {
      display: none;
    }

    .topic-card {
      min-width: 62vw;
      scroll-snap-align: start;
    }

    .install-action {
      flex-direction: column;
    }
  }

  @media (max-width: 768px) {
    .nav-links {
      display: none;
    }
    
    .mobile-menu-btn {
      display: block;
    }

    .nav-actions .btn {
      padding: 0 16px;
      height: 36px;
      font-size: 13px;
    }

    .rank-track {
      gap: 16px;
    }

    .rank-item {
      flex: 0 0 44vw;
    }
    
    .footer-top {
      flex-direction: column;
      gap: 24px;
    }
  }

  @media (max-width: 560px) {
    .hero-pills {
      grid-template-columns: 1fr;
    }
    
    .pill:last-child {
      grid-column: span 1;
    }

    .install-section {
      padding: 40px 24px;
    }
  }