/* ===== 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-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-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); }