/* ===== Navigation ===== */
      nav {
        position: fixed;
        top: 0; left: 0; right: 0;
        z-index: 100;
        display: flex;
        align-items: center;
        justify-content: space-between;
        padding: 0 28px;
        height: 68px;
        background: rgba(8,10,30,0.75);
        backdrop-filter: blur(20px);
        -webkit-backdrop-filter: blur(20px);
        border-bottom: 1px solid rgba(79,70,229,0.12);
        transition: background 0.3s;
      }

      .nav-logo {
        display: flex;
        align-items: center;
        gap: 12px;
        text-decoration: none;
        color: var(--text-primary);
      }

      .nav-logo-svg {
        width: 40px; height: 40px;
        flex-shrink: 0;
      }

      .nav-logo-text {
        display: flex;
        flex-direction: column;
        line-height: 1.2;
      }

      .nav-logo-en {
        font-size: 18px;
        font-weight: 800;
        letter-spacing: -0.02em;
        background: var(--gradient-wide);
        -webkit-background-clip: text;
        -webkit-text-fill-color: transparent;
        background-clip: text;
      }

      .nav-logo-zh {
        font-size: 11px;
        font-weight: 600;
        color: var(--text-muted);
        letter-spacing: 0.06em;
        -webkit-text-fill-color: var(--text-muted);
      }

      .nav-links {
        display: flex;
        gap: 6px;
        align-items: center;
      }

      .nav-menu-panel {
        display: flex;
        gap: 6px;
        align-items: center;
      }

      .nav-menu-toggle {
        display: none;
        position: relative;
        width: 44px;
        height: 44px;
        border: 1px solid rgba(148,163,184,0.18);
        border-radius: 14px;
        background:
          linear-gradient(145deg, rgba(17,20,51,0.92), rgba(8,10,30,0.88));
        color: var(--text-primary);
        cursor: pointer;
        touch-action: manipulation;
        transition: border-color 0.2s ease, background 0.2s ease, transform 0.2s ease;
      }

      .nav-menu-toggle:hover {
        border-color: rgba(34,211,238,0.34);
        background: rgba(34,211,238,0.1);
      }

      .nav-menu-toggle:focus-visible {
        outline: 3px solid rgba(34,211,238,0.34);
        outline-offset: 3px;
      }

      .nav-menu-toggle span {
        position: absolute;
        left: 12px;
        width: 18px;
        height: 2px;
        border-radius: 999px;
        background: currentColor;
        transition: transform 0.2s ease, opacity 0.2s ease, top 0.2s ease;
      }

      .nav-menu-toggle span:nth-child(1) { top: 14px; }
      .nav-menu-toggle span:nth-child(2) { top: 21px; }
      .nav-menu-toggle span:nth-child(3) { top: 28px; }

      .nav-menu-toggle[aria-expanded="true"] span:nth-child(1) {
        top: 21px;
        transform: rotate(45deg);
      }

      .nav-menu-toggle[aria-expanded="true"] span:nth-child(2) {
        opacity: 0;
      }

      .nav-menu-toggle[aria-expanded="true"] span:nth-child(3) {
        top: 21px;
        transform: rotate(-45deg);
      }

      .nav-links a {
        color: var(--text-secondary);
        text-decoration: none;
        font-size: 14px;
        font-weight: 500;
        padding: 8px 16px;
        border-radius: var(--radius-xs);
        transition: all 0.2s;
      }

      .nav-links a:hover { color: var(--text-primary); background: rgba(79,70,229,0.1); }

      .nav-product-link {
        margin-right: 8px;
        border: 1px solid rgba(34,211,238,0.18);
        background: rgba(34,211,238,0.08);
        color: var(--text-primary) !important;
        font-weight: 800 !important;
      }

      .nav-product-link:hover,
      .nav-product-link.section-active {
        border-color: rgba(34,211,238,0.34);
        background: rgba(34,211,238,0.14);
        box-shadow: 0 8px 24px rgba(34,211,238,0.12);
      }

      .nav-link-divider {
        width: 1px;
        height: 24px;
        margin: 0 12px 0 2px;
        background: linear-gradient(180deg, transparent, rgba(148,163,184,0.38), transparent);
      }

      .nav-section-link {
        color: var(--text-secondary);
      }

      .nav-cta {
        background: var(--gradient-main);
        color: white !important;
        font-weight: 600 !important;
        padding: 8px 22px !important;
        border-radius: var(--radius-xs) !important;
        box-shadow: 0 4px 16px rgba(79,70,229,0.3);
      }

      .nav-cta:hover { opacity: 0.92; transform: translateY(-1px); }

      @media (max-width: 920px) {
        nav {
          padding: 0 18px;
        }

        .nav-links {
          gap: 8px;
        }

        .nav-menu-toggle {
          display: inline-flex;
          flex: 0 0 auto;
        }

        .nav-menu-panel {
          position: fixed;
          top: 76px;
          left: 16px;
          right: 16px;
          z-index: 120;
          display: grid;
          grid-template-columns: 1fr;
          gap: 8px;
          padding: 12px;
          border: 1px solid rgba(148,163,184,0.18);
          border-radius: 22px;
          background:
            radial-gradient(circle at 10% 0%, rgba(34,211,238,0.16), transparent 34%),
            linear-gradient(145deg, rgba(17,20,51,0.96), rgba(8,10,30,0.96));
          box-shadow: 0 24px 70px rgba(0,0,0,0.36);
          backdrop-filter: blur(18px);
          -webkit-backdrop-filter: blur(18px);
          opacity: 0;
          transform: translateY(-8px);
          pointer-events: none;
          visibility: hidden;
          transition: opacity 0.2s ease, transform 0.2s ease, visibility 0.2s ease;
        }

        .nav-menu-panel.is-open {
          opacity: 1;
          transform: translateY(0);
          pointer-events: auto;
          visibility: visible;
        }

        .nav-menu-panel a {
          display: flex !important;
          align-items: center;
          min-height: 46px;
          width: 100%;
          padding: 12px 14px;
          border: 1px solid rgba(148,163,184,0.1);
          border-radius: 14px;
          background: rgba(255,255,255,0.035);
          font-weight: 800;
        }

        .nav-product-link {
          margin-right: 0;
        }

        .nav-link-divider {
          display: none;
        }
      }

      @media (max-width: 540px) {
        nav {
          padding: 0 12px;
        }

        .nav-logo-svg {
          width: 36px;
          height: 36px;
        }

        .nav-logo-en {
          font-size: 16px;
        }

        .nav-cta {
          padding: 8px 12px !important;
          font-size: 13px !important;
        }
      }

      @media (prefers-reduced-motion: reduce) {
        .nav-menu-toggle,
        .nav-menu-toggle span,
        .nav-menu-panel {
          transition: none;
        }
      }