:root {
      --primary: #003087;
      --secondary: #4b5e7a;
      --accent: #00a3e0;
      --bg-light: #f5f6f5;
      --text-dark: #1a1a1a;
      --text-muted: #5c6b80;
      --shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
      --transition: all 0.3s ease-in-out;
    }

    body {
      font-family: 'Roboto', system-ui, -apple-system, sans-serif;
      background: #fff;
      color: var(--text-dark);
      line-height: 1.7;
      overflow-x: hidden;
    }

    /* Navbar */
    .navbar {
      background: #fff;
      box-shadow: var(--shadow);
      padding: 1.25rem 0;
      position: sticky;
      top: 0;
      z-index: 1000;
    }

    .navbar-brand {
      font-weight: 700;
      font-size: 1.75rem;
      color: var(--primary) !important;
      display: flex;
      align-items: center;
      gap: 0.75rem;
    }

    .navbar-brand img {
      height: 36px;
    }

    .nav-link {
      color: var(--text-dark) !important;
      font-weight: 500;
      font-size: 1.1rem;
      padding: 0.5rem 1rem;
      position: relative;
      transition: var(--transition);
    }

    .nav-link::after {
      content: '';
      position: absolute;
      width: 0;
      height: 2px;
      bottom: 0;
      left: 0;
      background-color: var(--primary);
      transition: width 0.3s ease;
    }

    .nav-link:hover::after,
    .nav-link.active::after {
      width: 100%;
    }

    .nav-link:hover,
    .nav-link.active {
      color: var(--primary) !important;
    }


    /* Main Content */
    .hero-section {
      max-width: 1000px;
      margin: 0 auto;
      text-align: center;
      padding: 4rem 1rem;
      background: linear-gradient(180deg, #e9ecef 0%, #fff 100%);
      border-radius: 12px;
    }

    .hero-section h1 {
      font-size: 3rem;
      font-weight: 700;
      color: var(--primary);
      margin-bottom: 1.5rem;
    }

    .form-section {
      background: #fff;
      border-radius: 12px;
      padding: 2.5rem;
      box-shadow: var(--shadow);
      margin: 2rem auto;
      max-width: 900px;
    }

    .form-label {
      font-weight: 500;
      color: var(--text-dark);
      font-size: 1.1rem;
    }

    .form-control,
    .form-select {
      border-radius: 10px;
      border: 1px solid #ced4da;
      padding: 0.75rem;
      transition: var(--transition);
    }

    .form-control:focus,
    .form-select:focus {
      border-color: var(--accent);
      box-shadow: 0 0 0 0.25rem rgba(0, 163, 224, 0.2);
    }

    .btn-primary {
      background-color: var(--primary);
      border: none;
      border-radius: 10px;
      padding: 0.9rem 2rem;
      font-weight: 600;
      font-size: 1.1rem;
      transition: var(--transition);
    }

    .btn-primary:hover {
      background-color: var(--accent);
      transform: translateY(-3px);
    }

    .username-box {
      font-size: 1.15rem;
      font-weight: 500;
      border-radius: 10px;
      padding: 1rem;
      transition: var(--transition);
    }

    .username-box:hover {
      background-color: var(--bg-light);
      transform: scale(1.02);
    }

    .copy-btn {
      cursor: pointer;
      background-color: var(--bg-light) !important;
      transition: var(--transition);
    }

    .copy-btn:hover {
      background-color: var(--accent) !important;
      color: #fff !important;
    }

    .badge-category {
      font-size: 1rem;
      background-color: var(--accent);
      color: #fff;
      padding: 0.5rem 1rem;
      border-radius: 8px;
    }

    /* Footer */
    .footer {
      background: var(--primary);
      color: #fff;
      padding: 3rem 0;
    }

    .footer h5 {
      color: #fff;
      font-weight: 600;
      margin-bottom: 1.5rem;
    }

    .footer a {
      color: #d0e6ff;
      text-decoration: none;
      transition: var(--transition);
    }

    .footer a:hover {
      color: #fff;
      text-decoration: underline;
    }

    /* Animations */
    @keyframes slideIn {
      from { opacity: 0; transform: translateY(20px); }
      to { opacity: 1; transform: translateY(0); }
    }

    .slide-in {
      animation: slideIn 0.6s ease forwards;
    }

    /* Responsive */
    @media (max-width: 768px) {
      .hero-section h1 {
        font-size: 2.25rem;
      }
      .navbar-brand {
        font-size: 1.5rem;
      }
      .form-section {
        padding: 1.5rem;
      }
    }
    .error-section {
      max-width: 800px;
      margin: 4rem auto;
      text-align: center;
      padding: 2rem;
    }

    .error-section h1 {
      font-size: 6rem;
      font-weight: 700;
      color: var(--primary);
      margin-bottom: 1rem;
    }

    .error-section h2 {
      font-size: 2rem;
      font-weight: 500;
      color: var(--text-dark);
      margin-bottom: 1.5rem;
    }