:root {
      --blue-dark: #071e3d;
      --blue-main: #0f3d7a;
      --blue-soft: #e4edf9;
      --card-border: #d4deef;
      --text-main: #222;
      --text-sub: #555;
      --bg-page: #f3f6fb;
      --accent: #27a4ff;
      --accent-soft: #e3f4ff;
    }

    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
      background: var(--bg-page);
      color: var(--text-main);
      line-height: 1.6;
    }
    a { color: var(--accent); text-decoration: none; }
    a:hover { text-decoration: underline; }

    .page {
      max-width: 1120px;
      margin: 0 auto;
      padding: 0 16px 56px;
    }

    /* Top bar */
    .topbar {
      background: linear-gradient(90deg, #021127, var(--blue-main));
      color: #f5f7ff;
      padding: 10px 20px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      border-radius: 0 0 12px 12px;
      margin-bottom: 18px;
      box-shadow: 0 6px 16px rgba(0,0,0,0.25);
    }
    .topbar-left {
      display: flex;
      align-items: center;
      gap: 10px;
      font-weight: 600;
    }
    .topbar-left img.logo-mark {
      height: 28px;
      width: 28px;
      border-radius: 7px;
      background: #fff;
      padding: 2px;
    }
    .topbar-title {
      font-size: 16px;
      letter-spacing: 0.03em;
    }

    .lang-switch {
      font-size: 12px;
      display: inline-flex;
      align-items: center;
      flex-wrap: wrap;
      gap: 4px;
      background: rgba(3,18,40,0.6);
      padding: 4px 8px;
      border-radius: 999px;
      border: 1px solid rgba(255,255,255,0.15);
      max-width: 100%;
      justify-content: flex-end;
    }
    .lang-pill,
    .lang-link {
      padding: 2px 6px;
      border-radius: 999px;
      white-space: nowrap;
    }
    .lang-pill {
      cursor: default;
      background: #f5f7ff;
      color: #10213a;
      font-weight: 600;
    }
    .lang-link {
      color: #dde6ff;
      cursor: pointer;
      border: 1px solid transparent;
    }
    .lang-link:hover {
      border-color: rgba(221,230,255,0.7);
    }

    /* Hero */
    .hero-shell {
      background: radial-gradient(circle at top left, #374b8c 0, #071e3d 60%, #040812 100%);
      border-radius: 18px;
      padding: 26px 24px 28px;
      color: #f5f7ff;
      box-shadow: 0 18px 35px rgba(5,16,40,0.55);
      position: relative;
      overflow: hidden;
    }
    .hero-shell::before {
      content: "";
      position: absolute;
      inset: 0;
      background-image: radial-gradient(circle at 20% 0, rgba(111,207,255,0.22), transparent 55%),
                        radial-gradient(circle at 80% 100%, rgba(0,255,163,0.18), transparent 55%);
      opacity: 0.9;
      pointer-events: none;
    }
    .hero-inner {
      position: relative;
      display: flex;
      flex-wrap: wrap;
      gap: 28px;
      align-items: center;
      z-index: 1;
    }

    .hero-copy {
      flex: 1 1 320px;
      min-width: 260px;
    }
    .hero-title {
      font-size: 32px;
      font-weight: 700;
      margin-bottom: 10px;
    }
    .hero-subtitle {
      font-size: 15px;
      max-width: 520px;
      color: #e2e7ff;
      margin-bottom: 14px;
    }
    .hero-text {
      font-size: 13px;
      color: #c5d2ff;
      max-width: 560px;
    }
    .hero-text p { margin-bottom: 6px; }

    .hero-cta {
      margin-top: 16px;
      display: flex;
      flex-wrap: wrap;
      gap: 10px;
    }
    .btn {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      padding: 8px 18px;
      border-radius: 999px;
      font-size: 13px;
      border: 1px solid transparent;
      cursor: pointer;
      white-space: nowrap;
    }
    .btn-primary {
      background: #20a4ff;
      border-color: #1a8bdd;
      color: #041221;
      font-weight: 600;
      box-shadow: 0 8px 16px rgba(0,0,0,0.35);
    }
    .btn-primary:hover {
      background: #3ab4ff;
    }
    .btn-ghost {
      background: transparent;
      border-color: rgba(208,223,255,0.7);
      color: #e1e6ff;
    }
    .btn-ghost:hover {
      background: rgba(8,24,64,0.7);
    }

    .hero-board {
      flex: 0 0 320px;
      max-width: 360px;
      margin-left: auto;
    }
    .hero-board-inner {
      background: rgba(8,20,48,0.92);
      border-radius: 20px;
      padding: 16px 18px 20px;
      box-shadow: 0 10px 28px rgba(0,0,0,0.65);
    }
    .hero-board-inner img {
      width: 100%;
      border-radius: 14px;
      display: block;
    }

    main { margin-top: 26px; }

    h2.section-title {
      font-size: 20px;
      margin-bottom: 12px;
      color: #182338;
    }

    .section {
      margin-top: 26px;
      background: #ffffff;
      border-radius: 14px;
      padding: 18px 18px 20px;
      box-shadow: 0 4px 10px rgba(15,23,42,0.06);
      border: 1px solid #e0e6f3;
      font-size: 14px;
      color: var(--text-sub);
    }

    /* Main features */
    .feature-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
      gap: 14px;
      margin-top: 8px;
    }
    .feature-card {
      border-radius: 12px;
      background: #f8fbff;
      border: 1px solid var(--card-border);
      padding: 12px 13px 12px;
    }
    .feature-card h3 {
      font-size: 14px;
      margin-bottom: 6px;
      color: #1d2840;
    }
    .feature-card ul { padding-left: 18px; }

    /* Hardware overview table */
    .spec-table {
      width: 100%;
      border-collapse: collapse;
      font-size: 13px;
      margin-top: 4px;
    }
    .spec-table thead th {
      background: var(--blue-main);
      color: #f5f7ff;
      padding: 6px 9px;
      font-weight: 600;
      font-size: 13px;
    }
    .spec-table tbody th,
    .spec-table tbody td {
      border-bottom: 1px solid #dde4f3;
      padding: 6px 9px;
      text-align: left;
    }
    .spec-table tbody th {
      width: 170px;
      background: #f4f6fc;
      color: #444f6b;
      font-weight: 500;
    }

    /* Connectors */
    .pinout-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
      gap: 14px;
      margin-top: 8px;
      font-size: 13px;
    }
    .pin-card {
      background: #f9fbff;
      border-radius: 12px;
      border: 1px solid var(--card-border);
      padding: 11px 12px;
    }
    .pin-card strong { display: block; margin-bottom: 4px; color: #1e2a44; }
    .pin-card ul { padding-left: 18px; }

    /* Quick start */
    .qs-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
      gap: 14px;
      margin-top: 10px;
    }
    .qs-step {
      background: #f8fbff;
      border-radius: 12px;
      border: 1px solid var(--card-border);
      padding: 12px 13px 12px 14px;
      position: relative;
      overflow: hidden;
    }
    .qs-step-number {
      position: absolute;
      right: 10px;
      bottom: -8px;
      font-size: 46px;
      font-weight: 800;
      color: rgba(44,82,130,0.09);
    }
    .qs-step h3 {
      font-size: 14px;
      margin-bottom: 6px;
      color: #182338;
    }
    .qs-step ul { padding-left: 18px; }

    /* FAQ */
    .faq-item {
      padding: 8px 0;
      border-top: 1px solid #e3e7f2;
      font-size: 13px;
    }
    .faq-item:first-of-type { border-top: none; }
    .faq-q { font-weight: 600; color: #1b2640; margin-bottom: 2px; }

    footer.site-footer {
      margin-top: 26px;
      padding: 14px 12px 0;
      font-size: 12px;
      color: #6b7280;
      text-align: center;
    }
    footer.site-footer a { color: #4f7bd6; }

    @media (max-width: 768px) {
      .hero-shell {
        border-radius: 0 0 18px 18px;
      }
      .topbar {
        border-radius: 0 0 10px 10px;
      }
      .hero-title { font-size: 26px; }
      .hero-board { max-width: 280px; margin: 12px auto 0; }
      .lang-switch { margin-top: 8px; }
    }