/* roulang page: index */
:root {
      --ink: #14243b;
      --muted: #65758b;
      --blue: #1769aa;
      --cyan: #27a9c9;
      --pale: #eef7fb;
      --line: #dce8f0;
      --white: #ffffff;
      --coral: #ec6b62;
      --radius: 18px;
      --shadow: 0 14px 38px rgba(20, 56, 86, .10);
      --shadow-lg: 0 24px 60px rgba(20, 56, 86, .16);
    }
    * { box-sizing: border-box; margin: 0; padding: 0; }
    html { scroll-behavior: smooth; }
    body {
      color: var(--ink);
      background: #fbfdff;
      font-family: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
      line-height: 1.7;
      letter-spacing: 0;
    }
    a { color: inherit; text-decoration: none; }
    img { display: block; width: 100%; object-fit: cover; }
    button, input { font: inherit; }
    button { cursor: pointer; border: 0; }
    :focus-visible { outline: 3px solid rgba(39,169,201,.45); outline-offset: 3px; }
    .container { width: min(1180px, calc(100% - 40px)); margin: 0 auto; }
    .site-header {
      position: sticky; top: 0; z-index: 30; background: rgba(255,255,255,.94);
      backdrop-filter: blur(16px); border-bottom: 1px solid rgba(220,232,240,.8);
    }
    .nav-shell { min-height: 76px; display: flex; align-items: center; justify-content: space-between; gap: 24px; }
    .brand { display: inline-flex; align-items: center; gap: 12px; min-width: 240px; }
    .brand-mark {
      width: 40px; height: 40px; display: grid; place-items: center; color: #fff; font-weight: 800;
      border-radius: 12px; background: var(--blue); box-shadow: 0 8px 18px rgba(23,105,170,.22);
    }
    .brand-name { font-size: 15px; font-weight: 800; color: var(--ink); white-space: nowrap; }
    .nav-links { display: flex; align-items: center; gap: 24px; }
    .nav-links a { color: var(--muted); font-size: 14px; font-weight: 600; transition: color .2s ease; }
    .nav-links a:hover, .nav-links a.active { color: var(--blue); }
    .nav-cta, .btn-primary {
      display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: 44px;
      padding: 0 20px; border-radius: 10px; color: #fff; background: var(--blue);
      font-size: 14px; font-weight: 700; box-shadow: 0 9px 20px rgba(23,105,170,.18); transition: .2s ease;
    }
    .nav-cta:hover, .btn-primary:hover { background: #0f568e; transform: translateY(-2px); }
    .menu-toggle { display: none; width: 42px; height: 42px; border-radius: 10px; background: var(--pale); color: var(--blue); }
    .hero {
      position: relative; overflow: hidden; min-height: 590px; display: flex; align-items: center;
      background: #eaf5fa;
    }
    .hero::before {
      content: ""; position: absolute; inset: 0; background:
      linear-gradient(90deg, rgba(234,245,250,.98) 0%, rgba(234,245,250,.91) 44%, rgba(234,245,250,.20) 100%),
      url("https://images.unsplash.com/photo-1516321318423-f06f85e504b3?auto=format&fit=crop&w=1800&q=85") center/cover;
    }
    .hero-inner { position: relative; z-index: 1; padding: 90px 0; }
    .hero-copy { max-width: 680px; }
    .eyebrow, .section-kicker {
      display: inline-flex; align-items: center; gap: 8px; color: var(--blue); font-size: 12px; font-weight: 800;
      letter-spacing: .08em; text-transform: uppercase;
    }
    .eyebrow::before, .section-kicker::before { content: ""; width: 24px; height: 2px; background: var(--cyan); }
    h1 { margin-top: 16px; color: var(--ink); font-size: clamp(38px, 5vw, 66px); line-height: 1.15; font-weight: 900; letter-spacing: 0; }
    h1 em { color: var(--coral); font-style: normal; }
    .hero-sub { margin-top: 20px; max-width: 620px; color: #40566c; font-size: 18px; line-height: 1.9; }
    .hero-actions { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 30px; }
    .btn-secondary {
      display: inline-flex; align-items: center; justify-content: center; min-height: 44px; padding: 0 20px;
      color: var(--blue); border: 1px solid #b9d5e3; background: rgba(255,255,255,.78); border-radius: 10px;
      font-size: 14px; font-weight: 700; transition: .2s ease;
    }
    .btn-secondary:hover { border-color: var(--blue); background: #fff; transform: translateY(-2px); }
    .hero-note { display: flex; flex-wrap: wrap; gap: 20px; margin-top: 34px; color: var(--muted); font-size: 13px; }
    .hero-note strong { color: var(--ink); font-size: 18px; margin-right: 5px; }
    section { padding: 92px 0; }
    .section-head { display: flex; justify-content: space-between; align-items: end; gap: 24px; margin-bottom: 32px; }
    .section-title { margin-top: 8px; font-size: clamp(26px, 3vw, 38px); line-height: 1.25; font-weight: 850; }
    .section-desc { max-width: 680px; margin-top: 12px; color: var(--muted); font-size: 15px; }
    .text-link { color: var(--blue); font-size: 14px; font-weight: 700; white-space: nowrap; }
    .text-link:hover { color: var(--coral); }
    .soft-section { background: var(--pale); }
    .content-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 18px; }
    .video-card, .topic-card, .quote-card, .resource-card {
      overflow: hidden; border: 1px solid var(--line); border-radius: var(--radius); background: #fff;
      box-shadow: var(--shadow); transition: transform .22s ease, box-shadow .22s ease, border-color .22s ease;
    }
    .video-card:hover, .topic-card:hover, .quote-card:hover, .resource-card:hover { transform: translateY(-5px); border-color: #b8d9e8; box-shadow: var(--shadow-lg); }
    .thumb { position: relative; aspect-ratio: 16/10; overflow: hidden; background: #dcebf2; }
    .thumb img { height: 100%; transition: transform .4s ease; }
    .video-card:hover .thumb img { transform: scale(1.05); }
    .thumb::after { content: ""; position: absolute; inset: 0; background: linear-gradient(180deg, transparent 42%, rgba(10,31,48,.52)); }
    .badge { position: absolute; top: 12px; left: 12px; z-index: 1; padding: 3px 8px; color: #fff; border-radius: 6px; background: var(--coral); font-size: 11px; font-weight: 800; }
    .duration { position: absolute; right: 12px; bottom: 10px; z-index: 1; color: #fff; font-size: 12px; font-weight: 700; }
    .video-body { padding: 16px; }
    .video-title { min-height: 50px; font-size: 15px; line-height: 1.6; font-weight: 800; }
    .meta-row { display: flex; align-items: center; justify-content: space-between; gap: 8px; margin-top: 10px; color: var(--muted); font-size: 12px; }
    .rating { color: #e29936; font-weight: 800; }
    .feature-strip { display: grid; grid-template-columns: 1.3fr 1fr 1fr; gap: 18px; }
    .feature-panel { min-height: 260px; padding: 28px; border-radius: var(--radius); color: #fff; background: var(--ink); box-shadow: var(--shadow-lg); }
    .feature-panel:nth-child(2) { background: var(--blue); }
    .feature-panel:nth-child(3) { color: var(--ink); background: #dff2f5; }
    .feature-panel h3 { font-size: 22px; line-height: 1.35; }
    .feature-panel p { margin-top: 14px; color: inherit; opacity: .82; font-size: 14px; }
    .feature-index { display: block; margin-bottom: 34px; color: var(--cyan); font-size: 13px; font-weight: 900; }
    .topic-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
    .topic-card { padding: 24px; min-height: 190px; }
    .topic-icon { width: 42px; height: 42px; display: grid; place-items: center; border-radius: 12px; color: var(--blue); background: var(--pale); font-weight: 900; }
    .topic-card h3 { margin-top: 18px; font-size: 18px; }
    .topic-card p { margin-top: 8px; color: var(--muted); font-size: 14px; }
    .metric-band { background: var(--ink); color: #fff; }
    .metrics { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; }
    .metric { padding-right: 20px; border-right: 1px solid rgba(255,255,255,.16); }
    .metric:last-child { border-right: 0; }
    .metric strong { display: block; color: #fff; font-size: 38px; line-height: 1.1; }
    .metric span { display: block; margin-top: 8px; color: #b8cad8; font-size: 13px; }
    .steps { display: grid; grid-template-columns: repeat(4, 1fr); gap: 0; border-top: 1px solid var(--line); }
    .step { position: relative; padding: 28px 24px 20px 0; border-bottom: 1px solid var(--line); }
    .step:not(:last-child) { margin-right: 24px; border-right: 1px solid var(--line); }
    .step-no { color: var(--cyan); font-size: 13px; font-weight: 900; }
    .step h3 { margin-top: 10px; font-size: 17px; }
    .step p { margin-top: 8px; color: var(--muted); font-size: 14px; }
    .rank-layout { display: grid; grid-template-columns: 1.15fr .85fr; gap: 24px; align-items: start; }
    .rank-list { border-top: 1px solid var(--line); }
    .rank-item { display: grid; grid-template-columns: 46px 1fr auto auto; gap: 18px; align-items: center; padding: 16px 0; border-bottom: 1px solid var(--line); }
    .rank-number { color: var(--cyan); font-size: 20px; font-weight: 900; }
    .rank-name { font-size: 14px; font-weight: 800; }
    .rank-tag { padding: 3px 8px; color: var(--blue); background: var(--pale); border-radius: 5px; font-size: 11px; font-weight: 800; }
    .rank-score { color: #d68725; font-size: 13px; font-weight: 800; }
    .quote-card { padding: 26px; }
    .quote-card p { color: #41586c; font-size: 15px; }
    .quote-user { display: flex; align-items: center; gap: 10px; margin-top: 22px; }
    .avatar { width: 36px; height: 36px; display: grid; place-items: center; border-radius: 50%; color: var(--blue); background: var(--pale); font-weight: 800; }
    .quote-user small { color: var(--muted); }
    .resource-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
    .resource-card { display: grid; grid-template-columns: 130px 1fr; }
    .resource-card img { height: 100%; min-height: 140px; }
    .resource-body { padding: 18px; }
    .resource-date { color: var(--blue); font-size: 11px; font-weight: 800; }
    .resource-body h3 { margin-top: 8px; font-size: 15px; line-height: 1.5; }
    .resource-body p { margin-top: 7px; color: var(--muted); font-size: 12px; }
    .faq-wrap { display: grid; grid-template-columns: .75fr 1.25fr; gap: 60px; align-items: start; }
    .faq-list { border-top: 1px solid var(--line); }
    details { padding: 18px 0; border-bottom: 1px solid var(--line); }
    summary { cursor: pointer; list-style: none; display: flex; justify-content: space-between; gap: 20px; font-size: 15px; font-weight: 800; }
    summary::-webkit-details-marker { display: none; }
    summary::after { content: "+"; color: var(--blue); font-size: 20px; line-height: 1; }
    details[open] summary::after { content: "−"; }
    details p { max-width: 680px; margin-top: 12px; color: var(--muted); font-size: 14px; }
    .cta-band { padding: 54px 0; background: #dff2f5; }
    .cta-inner { display: flex; align-items: center; justify-content: space-between; gap: 30px; }
    .cta-inner h2 { font-size: clamp(25px, 3vw, 38px); line-height: 1.25; }
    .cta-inner p { max-width: 620px; margin-top: 10px; color: var(--muted); font-size: 14px; }
    .site-footer { padding: 58px 0 24px; color: #b9c8d4; background: #102237; }
    .footer-grid { display: grid; grid-template-columns: 1.4fr 1fr 1fr 1fr; gap: 40px; }
    .footer-brand { color: #fff; }
    .footer-copy { margin-top: 14px; max-width: 300px; color: #9eb1c1; font-size: 13px; }
    .footer-title { color: #fff; font-size: 14px; font-weight: 800; }
    .footer-links { display: grid; gap: 9px; margin-top: 14px; font-size: 13px; }
    .footer-links a { transition: color .2s ease; }
    .footer-links a:hover { color: #fff; }
    .copyright { margin-top: 42px; padding-top: 20px; border-top: 1px solid rgba(255,255,255,.12); color: #8499aa; font-size: 12px; }
    @media (max-width: 1024px) {
      .content-grid { grid-template-columns: repeat(3, 1fr); }
      .feature-strip { grid-template-columns: 1fr 1fr; }
      .feature-panel:first-child { grid-column: span 2; }
      .rank-layout, .faq-wrap { grid-template-columns: 1fr; gap: 34px; }
    }
    @media (max-width: 768px) {
      .container { width: min(100% - 32px, 620px); }
      .nav-links, .nav-cta { display: none; }
      .menu-toggle { display: grid; place-items: center; }
      .nav-shell.open .nav-links {
        position: absolute; top: 76px; left: 0; right: 0; display: grid; gap: 0; padding: 12px 20px 18px;
        background: #fff; border-bottom: 1px solid var(--line); box-shadow: var(--shadow);
      }
      .nav-shell.open .nav-links a { padding: 10px 0; }
      .hero { min-height: 620px; }
      .hero::before { background: linear-gradient(90deg, rgba(234,245,250,.98), rgba(234,245,250,.74)), url("https://images.unsplash.com/photo-1516321318423-f06f85e504b3?auto=format&fit=crop&w=1200&q=80") center/cover; }
      section { padding: 68px 0; }
      .section-head { display: block; }
      .section-head .text-link { display: inline-block; margin-top: 16px; }
      .content-grid { grid-template-columns: repeat(2, 1fr); }
      .topic-grid, .resource-grid { grid-template-columns: 1fr 1fr; }
      .metrics { grid-template-columns: repeat(2, 1fr); gap: 24px 14px; }
      .metric:nth-child(2) { border-right: 0; }
      .steps { grid-template-columns: repeat(2, 1fr); }
      .step:nth-child(2) { border-right: 0; margin-right: 0; }
      .step:nth-child(3), .step:nth-child(4) { border-top: 1px solid var(--line); }
      .footer-grid { grid-template-columns: repeat(2, 1fr); }
      .cta-inner { display: block; }
      .cta-inner .btn-primary { margin-top: 22px; }
    }
    @media (max-width: 520px) {
      .container { width: min(100% - 28px, 430px); }
      .brand { min-width: 0; }
      .brand-name { max-width: 190px; overflow: hidden; text-overflow: ellipsis; }
      h1 { font-size: 38px; }
      .hero-sub { font-size: 16px; }
      .hero-note { gap: 12px; }
      .content-grid, .topic-grid, .resource-grid, .feature-strip { grid-template-columns: 1fr; }
      .feature-panel:first-child { grid-column: auto; }
      .rank-item { grid-template-columns: 34px 1fr auto; gap: 10px; }
      .rank-tag { display: none; }
      .steps { grid-template-columns: 1fr; }
      .step, .step:nth-child(2) { margin-right: 0; padding-right: 0; border-right: 0; }
      .step:not(:first-child) { border-top: 1px solid var(--line); }
      .footer-grid { grid-template-columns: 1fr 1fr; gap: 30px 18px; }
      .footer-grid > div:first-child { grid-column: span 2; }
    }