#site-header {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      z-index: 1000;
      transition: transform 0.35s ease, box-shadow 0.35s ease;
    }

    #site-header.scrolled-down {
      box-shadow: 0 2px 12px rgba(0,0,0,0.12);
    }

    /* ── Announcement bar ── */
    #announcement-bar {
      background: linear-gradient(90deg, #0d6e8a 0%, #1a9db8 50%, #0d6e8a 100%);
      padding: 10px 20px;
      text-align: center;
      overflow: hidden;
      max-height: 44px;
      transition: max-height 0.4s ease, padding 0.4s ease, opacity 0.3s ease;
      opacity: 1;
    }

    #site-header.hide-bar #announcement-bar {
      max-height: 0;
      padding: 0 20px;
      opacity: 0;
    }

    .announcement-inner {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 24px;
      flex-wrap: wrap;
    }

    .announcement-inner span {
      color: #ffffff;
      font-size: 13.5px;
      font-weight: 600;
      letter-spacing: 0.01em;
      white-space: nowrap;
    }

    .announcement-divider {
      color: rgba(255,255,255,0.6);
      font-size: 18px;
      font-weight: 300;
    }

    /* ── Main nav ── */
    #main-nav {
      background: #ffffff;
      border-bottom: 1px solid #e8e8e8;
      padding: 0 40px;
      height: 70px;
      display: flex;
      align-items: center;
      justify-content: space-between;
    }

    /* Logo */
    .nav-logo {
      display: flex;
      align-items: center;
      gap: 4px;
      text-decoration: none;
      flex-shrink: 0;
    }

    .logo-text {
      font-size: 20px;
      font-weight: 700;
      letter-spacing: 0.12em;
      color: #1a1a2e;
      text-transform: uppercase;
    }

    .logo-dna-wrap {
      position: relative;
      width: 38px;
      height: 48px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    .logo-dna-wrap svg {
      width: 38px;
      height: 48px;
    }

    .logo-dna-label {
      position: absolute;
      bottom: 2px;
      right: 0;
      font-size: 8px;
      font-weight: 700;
      letter-spacing: 0.1em;
      color: #555;
    }

    /* Nav links */
    .nav-links {
      display: flex;
      align-items: center;
      gap: 8px;
      list-style: none;
    }

    .nav-links li a {
      text-decoration: none;
      color: #333;
      font-size: 15px;
      font-weight: 500;
      padding: 8px 14px;
      border-radius: 6px;
      transition: color 0.2s, background 0.2s;
      white-space: nowrap;
    }

    .nav-links li a:hover {
      color: #1a9db8;
      background: #f0fafd;
    }

    .nav-links li a.active {
      font-weight: 700;
      color: #1a1a2e;
    }

    /* Login button */
    .btn-login {
      display: flex;
      align-items: center;
      gap: 8px;
      background: #1aada8;
      color: #fff;
      border: none;
      border-radius: 50px;
      padding: 10px 22px;
      font-size: 15px;
      font-weight: 600;
      cursor: pointer;
      text-decoration: none;
      transition: background 0.2s, transform 0.15s;
      white-space: nowrap;
      flex-shrink: 0;
    }

    .btn-login:hover {
      background: #159490;
      transform: translateY(-1px);
    }

    .btn-login svg {
      width: 17px;
      height: 17px;
    }

    /* ── Hamburger ── */
    .hamburger {
      display: none;
      flex-direction: column;
      gap: 5px;
      cursor: pointer;
      padding: 4px;
      background: none;
      border: none;
    }

    .hamburger span {
      display: block;
      width: 24px;
      height: 2px;
      background: #333;
      border-radius: 2px;
      transition: all 0.3s;
    }

    .hamburger.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
    .hamburger.open span:nth-child(2) { opacity: 0; }
    .hamburger.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

    /* ── Mobile menu ── */
    #mobile-menu {
      display: none;
      background: #fff;
      border-top: 1px solid #eee;
      padding: 16px 24px 20px;
      flex-direction: column;
      gap: 4px;
    }

    #mobile-menu a {
      text-decoration: none;
      color: #333;
      font-size: 16px;
      font-weight: 500;
      padding: 11px 8px;
      border-bottom: 1px solid #f0f0f0;
      display: block;
      transition: color 0.2s;
    }

    #mobile-menu a:last-child { border-bottom: none; }
    #mobile-menu a:hover { color: #1a9db8; }

    #mobile-menu .btn-login-mobile {
      margin-top: 12px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      background: #1aada8;
      color: #fff;
      border-radius: 50px;
      padding: 12px 22px;
      font-weight: 600;
      border-bottom: none;
    }

    /* ── Demo content ── */
    .demo-content {
      margin-top: 114px;
      padding: 60px 40px;
      max-width: 700px;
      margin-left: auto;
      margin-right: auto;
    }

    .demo-content h1 {
      font-size: 28px;
      color: #1a1a2e;
      margin-bottom: 12px;
    }

    .demo-content p {
      color: #666;
      font-size: 16px;
      line-height: 1.7;
    }

    /* ── Responsive ── */
    @media (max-width: 900px) {
      #main-nav { padding: 0 20px; }
      .nav-links { display: none; }
      .btn-login { display: none; }
      .hamburger { display: flex; }
      #mobile-menu.open { display: flex; }
    }

    @media (max-width: 520px) {
      .announcement-inner span { font-size: 11.5px; }
      .announcement-divider { display: none; }
      .announcement-inner { gap: 6px; flex-direction: column; }
      #announcement-bar { max-height: 60px; padding: 8px 12px; }
      #site-header.hide-bar #announcement-bar { max-height: 0; padding: 0; }
    }