/* roulang page: index */
:root {
      --primary: #1E3A8A;
      --primary-light: #2563EB;
      --accent: #6366F1;
      --cyan: #06B6D4;
      --bg-base: #F8FAFC;
      --bg-card: #FFFFFF;
      --text-main: #0F172A;
      --text-muted: #334155;
      --text-light: #64748B;
      --border-color: #E2E8F0;
      --dark-surface: #0B0F19;
      --dark-card: #131B2E;
      --radius-sm: 6px;
      --radius-md: 10px;
      --radius-lg: 16px;
      --shadow-sm: 0 2px 8px -1px rgba(15, 23, 42, 0.04);
      --shadow-md: 0 8px 24px -4px rgba(15, 23, 42, 0.07);
      --shadow-lg: 0 16px 36px -6px rgba(15, 23, 42, 0.12);
    }
    * { box-sizing: border-box; margin: 0; padding: 0; }
    html { scroll-behavior: smooth; font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif; }
    body { background-color: var(--bg-base); color: var(--text-main); line-height: 1.6; font-size: 15px; -webkit-font-smoothing: antialiased; }
    a { color: inherit; text-decoration: none; transition: all 0.2s ease; }
    img { max-width: 100%; height: auto; display: block; }
    button, input, select, textarea { font-family: inherit; }
    
    .container { width: 100%; max-width: 1280px; margin: 0 auto; padding: 0 24px; }
    
    /* Top Bar */
    .top-bar { background-color: #0F172A; color: #94A3B8; font-size: 12px; border-bottom: 1px solid #1E293B; line-height: 36px; }
    .top-bar-inner { display: flex; justify-content: space-between; align-items: center; }
    .status-badge { display: inline-flex; align-items: center; gap: 6px; }
    .status-dot { width: 7px; height: 7px; background-color: #10B981; border-radius: 50%; box-shadow: 0 0 6px #10B981; }

    /* Main Nav */
    .site-header { position: sticky; top: 0; z-index: 100; background: rgba(255, 255, 255, 0.95); backdrop-filter: blur(12px); border-bottom: 1px solid var(--border-color); }
    .nav-inner { display: flex; align-items: center; justify-content: space-between; height: 72px; }
    .brand-logo { font-size: 19px; font-weight: 700; color: var(--primary); display: flex; align-items: center; gap: 10px; letter-spacing: -0.02em; }
    .brand-logo span { color: var(--text-main); }
    .brand-mark { width: 34px; height: 34px; background: linear-gradient(135deg, var(--primary), var(--accent)); border-radius: var(--radius-sm); display: flex; align-items: center; justify-content: center; color: #fff; font-weight: 800; font-size: 16px; }
    .nav-links { display: flex; gap: 28px; align-items: center; list-style: none; }
    .nav-link { font-weight: 500; font-size: 14px; color: var(--text-muted); position: relative; padding: 8px 0; }
    .nav-link:hover, .nav-link.active { color: var(--primary-light); }
    .nav-actions { display: flex; align-items: center; gap: 14px; }
    .btn { display: inline-flex; align-items: center; justify-content: center; font-weight: 600; font-size: 14px; border-radius: var(--radius-sm); padding: 10px 20px; cursor: pointer; transition: all 0.25s ease; border: 1px solid transparent; }
    .btn-primary { background-color: var(--primary); color: #fff; box-shadow: 0 4px 12px rgba(30, 58, 138, 0.2); }
    .btn-primary:hover { background-color: var(--primary-light); transform: translateY(-1px); }
    .btn-outline { border-color: var(--border-color); background: #fff; color: var(--text-muted); }
    .btn-outline:hover { border-color: var(--primary); color: var(--primary); }
    .btn-dark { background-color: var(--dark-surface); color: #fff; }
    .btn-dark:hover { background-color: #1E293B; }
    .menu-toggle { display: none; background: none; border: none; font-size: 24px; cursor: pointer; color: var(--text-main); }

    /* Section Base */
    .section-wrap { padding: 88px 0; border-bottom: 1px solid var(--border-color); position: relative; }
    .section-dark { background-color: var(--dark-surface); color: #fff; border-bottom-color: #1E293B; }
    .section-head { margin-bottom: 48px; }
    .section-head.center { text-align: center; max-width: 760px; margin-left: auto; margin-right: auto; }
    .section-tag { display: inline-block; font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.08em; color: var(--accent); background: rgba(99, 102, 241, 0.08); padding: 4px 12px; border-radius: 30px; margin-bottom: 12px; }
    .section-dark .section-tag { background: rgba(99, 102, 241, 0.2); color: #818CF8; }
    .section-title { font-size: 32px; font-weight: 700; line-height: 1.28; color: var(--text-main); letter-spacing: -0.02em; margin-bottom: 14px; }
    .section-dark .section-title { color: #fff; }
    .section-desc { font-size: 16px; color: var(--text-muted); line-height: 1.7; }
    .section-dark .section-desc { color: #94A3B8; }

    /* Section 1: Hero (API / Developer Stage) */
    .hero-sec { padding: 60px 0 80px; background: radial-gradient(circle at top right, rgba(99, 102, 241, 0.07), transparent 60%); }
    .hero-grid { display: grid; grid-template-columns: 1.1fr 0.9fr; gap: 48px; align-items: center; }
    .hero-title { font-size: 44px; font-weight: 800; line-height: 1.18; color: var(--text-main); margin-bottom: 20px; letter-spacing: -0.03em; }
    .hero-title span { color: var(--primary); }
    .hero-lead { font-size: 16px; color: var(--text-muted); line-height: 1.75; margin-bottom: 30px; }
    .hero-stats { display: flex; gap: 32px; margin-top: 36px; padding-top: 28px; border-top: 1px solid var(--border-color); }
    .hero-stat-num { font-size: 24px; font-weight: 700; color: var(--primary); }
    .hero-stat-lbl { font-size: 13px; color: var(--text-light); }
    .code-console { background: #0F172A; border-radius: var(--radius-md); box-shadow: var(--shadow-lg); overflow: hidden; border: 1px solid #334155; }
    .console-header { background: #1E293B; padding: 12px 16px; display: flex; align-items: center; gap: 8px; }
    .console-dot { width: 10px; height: 10px; border-radius: 50%; display: inline-block; }
    .dot-red { background-color: #EF4444; }
    .dot-yellow { background-color: #F59E0B; }
    .dot-green { background-color: #10B981; }
    .console-title { font-size: 12px; color: #94A3B8; font-family: monospace; margin-left: auto; }
    .console-body { padding: 22px; font-family: "JetBrains Mono", Consolas, Menlo, monospace; font-size: 13px; line-height: 1.65; color: #E2E8F0; overflow-x: auto; }
    .c-keyword { color: #F43F5E; }
    .c-prop { color: #38BDF8; }
    .c-str { color: #A7F3D0; }
    .c-num { color: #FBBF24; }

    /* Common Card Grid */
    .grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
    .grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; }
    .grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 32px; }

    .card { background: var(--bg-card); border-radius: var(--radius-md); border: 1px solid var(--border-color); padding: 28px; transition: transform 0.25s, box-shadow 0.25s, border-color 0.25s; }
    .card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); border-color: #CBD5E1; }
    .card-badge { display: inline-block; font-size: 11px; font-weight: 700; padding: 3px 8px; border-radius: 4px; background: #EEF2FF; color: var(--accent); margin-bottom: 14px; }
    .card-title { font-size: 18px; font-weight: 700; margin-bottom: 12px; color: var(--text-main); }
    .card-desc { font-size: 14px; color: var(--text-muted); line-height: 1.65; }

    /* Section 2: Overview */
    .overview-content { display: grid; grid-template-columns: 1fr 1fr; gap: 40px; align-items: center; }
    .param-list { list-style: none; margin-top: 24px; display: grid; gap: 14px; }
    .param-item { display: flex; align-items: flex-start; gap: 12px; font-size: 14px; color: var(--text-muted); }
    .param-bullet { width: 18px; height: 18px; background: #EEF2FF; border-radius: 50%; color: var(--accent); display: flex; align-items: center; justify-content: center; font-size: 11px; font-weight: 700; flex-shrink: 0; margin-top: 2px; }
    .overview-img-wrap { border-radius: var(--radius-lg); overflow: hidden; border: 1px solid var(--border-color); box-shadow: var(--shadow-md); }

    /* Section 5: Tech Philosophy */
    .arch-flow { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; margin-top: 36px; }
    .arch-step { background: var(--dark-card); border: 1px solid #1E293B; border-radius: var(--radius-md); padding: 24px; position: relative; }
    .arch-num { font-size: 12px; font-weight: 800; color: var(--cyan); letter-spacing: 0.1em; margin-bottom: 10px; }
    .arch-title { font-size: 16px; font-weight: 700; color: #fff; margin-bottom: 8px; }
    .arch-desc { font-size: 13px; color: #94A3B8; line-height: 1.6; }

    /* Section 7: Metrics */
    .metric-box { text-align: center; padding: 24px 16px; border-right: 1px solid var(--border-color); }
    .metric-box:last-child { border-right: none; }
    .metric-val { font-size: 40px; font-weight: 800; color: var(--primary); letter-spacing: -0.03em; line-height: 1.1; margin-bottom: 8px; font-family: monospace; }
    .metric-lbl { font-size: 14px; font-weight: 600; color: var(--text-main); margin-bottom: 4px; }
    .metric-sub { font-size: 12px; color: var(--text-light); }

    /* Section 10: Partners */
    .partner-grid { display: grid; grid-template-columns: repeat(6, 1fr); gap: 16px; }
    .partner-item { background: #fff; border: 1px solid var(--border-color); border-radius: var(--radius-sm); height: 72px; display: flex; align-items: center; justify-content: center; font-size: 13px; font-weight: 600; color: var(--text-light); filter: grayscale(1); opacity: 0.7; transition: all 0.2s; }
    .partner-item:hover { filter: grayscale(0); opacity: 1; border-color: var(--primary-light); color: var(--primary); }

    /* Section 11: FAQ Accordion */
    .faq-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; }
    .faq-item { background: #fff; border: 1px solid var(--border-color); border-radius: var(--radius-md); overflow: hidden; }
    .faq-question { padding: 18px 22px; font-size: 15px; font-weight: 600; cursor: pointer; display: flex; justify-content: space-between; align-items: center; user-select: none; }
    .faq-question::-webkit-details-marker { display: none; }
    .faq-icon { font-size: 18px; transition: transform 0.25s ease; color: var(--text-light); }
    details[open] .faq-icon { transform: rotate(45deg); color: var(--primary); }
    .faq-answer { padding: 0 22px 20px; font-size: 14px; color: var(--text-muted); line-height: 1.7; border-top: 1px solid #F1F5F9; margin-top: -6px; padding-top: 14px; }

    /* Section 12: Lead CTA */
    .cta-card { background: linear-gradient(135deg, #0F172A 0%, #1E3A8A 100%); border-radius: var(--radius-lg); padding: 56px 48px; color: #fff; display: grid; grid-template-columns: 1.2fr 0.8fr; gap: 40px; align-items: center; }
    .cta-form { background: #fff; border-radius: var(--radius-md); padding: 28px; color: var(--text-main); }
    .form-group { margin-bottom: 16px; }
    .form-label { display: block; font-size: 13px; font-weight: 600; margin-bottom: 6px; color: var(--text-muted); }
    .form-control { width: 100%; height: 42px; border: 1px solid var(--border-color); border-radius: var(--radius-sm); padding: 0 12px; font-size: 14px; outline: none; }
    .form-control:focus { border-color: var(--primary); ring: 2px rgba(30, 58, 138, 0.2); }
    .privacy-text { font-size: 12px; color: var(--text-light); margin-top: 12px; line-height: 1.5; }

    /* Footer */
    .site-footer { background: #0B0F19; color: #94A3B8; padding: 64px 0 32px; border-top: 1px solid #1E293B; font-size: 13px; }
    .footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 40px; margin-bottom: 48px; }
    .footer-brand { font-size: 18px; font-weight: 700; color: #fff; margin-bottom: 14px; display: inline-block; }
    .footer-col-title { font-size: 14px; font-weight: 600; color: #fff; margin-bottom: 18px; }
    .footer-links { list-style: none; display: grid; gap: 10px; }
    .footer-links a:hover { color: #fff; }
    .footer-bottom { border-top: 1px solid #1E293B; padding-top: 24px; display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 14px; }

    /* Responsive */
    @media (max-width: 1024px) {
      .hero-grid, .overview-content, .cta-card { grid-template-columns: 1fr; }
      .grid-4 { grid-template-columns: repeat(2, 1fr); }
      .grid-3 { grid-template-columns: repeat(2, 1fr); }
      .arch-flow { grid-template-columns: repeat(2, 1fr); }
      .partner-grid { grid-template-columns: repeat(3, 1fr); }
      .footer-grid { grid-template-columns: 1fr 1fr; }
    }
    @media (max-width: 768px) {
      .top-bar { display: none; }
      .nav-links, .nav-actions .btn-outline { display: none; }
      .menu-toggle { display: block; }
      .hero-title { font-size: 32px; }
      .section-title { font-size: 24px; }
      .grid-3, .grid-4, .grid-2, .faq-grid { grid-template-columns: 1fr; }
      .metric-box { border-right: none; border-bottom: 1px solid var(--border-color); }
      .cta-card { padding: 32px 20px; }
      .partner-grid { grid-template-columns: repeat(2, 1fr); }
      .footer-grid { grid-template-columns: 1fr; }
      
      /* Mobile Drawer */
      .nav-links.mobile-open {
        display: flex; flex-direction: column; position: absolute; top: 72px; left: 0; right: 0; background: #fff; border-bottom: 1px solid var(--border-color); padding: 24px; gap: 16px; box-shadow: var(--shadow-lg);
      }
    }