:root {
      --primary-color: #0d6efd;
      --secondary-color: #6c757d;
      --card-bg: rgba(255, 255, 255, 0.95);
      --text-dark: #212529;
      --text-light: #f8f9fa;
      --shadow: 0 8px 20px rgba(0, 0, 0, 0.15);
      --border-radius: 15px;
      --transition: all 0.3s ease;
    }

    body {
      background: linear-gradient(rgba(255, 255, 255, 0.85), rgba(255, 255, 255, 0.95)),
                  url('assets/img/aeroworks-pbb-cf.jpg') no-repeat center center fixed;
      background-size: cover;
      color: var(--text-dark);
      min-height: 100vh;
      display: flex;
      flex-direction: column;
    }

    .main-content {
      flex: 1;
    }

    .card {
      background: var(--card-bg);
      color: var(--text-dark);
      border: none;
      border-radius: var(--border-radius);
      box-shadow: var(--shadow);
      transition: var(--transition);
      margin-bottom: 1.5rem;
    }

    .card:hover {
      transform: translateY(-5px);
      box-shadow: 0 12px 25px rgba(0, 0, 0, 0.2);
    }

    .card-header {
      font-weight: 600;
      font-size: clamp(1.1rem, 2.5vw, 1.4rem);
      border-radius: var(--border-radius) var(--border-radius) 0 0;
      background-color: var(--primary-color);
      color: var(--text-light);
      padding: 1rem 1.25rem;
    }

    .list-group-item {
      border: none;
      padding: 0.75rem 1.25rem;
      border-bottom: 1px solid rgba(0, 0, 0, 0.05);
    }

    .list-group-item:last-child {
      border-bottom: none;
    }

    .list-group-item a {
      display: block;
      width: 100%;
      padding: 0.5rem 0;
      color: var(--text-dark);
      text-decoration: none;
      transition: var(--transition);
      font-size: clamp(0.9rem, 2vw, 1rem);
    }

    .list-group-item a:hover {
      background-color: rgba(13, 110, 253, 0.1);
      border-radius: 8px;
      padding-left: 10px;
      color: var(--primary-color);
      font-weight: 500;
    }

    header {
      background-color: rgba(248, 249, 250, 0.95);
      backdrop-filter: blur(5px);
      border-bottom: 1px solid rgba(0, 0, 0, 0.1);
    }

    header img {
      max-height: 80px;
      height: auto;
      width: auto;
    }

    .header-content {
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      padding: 1rem 0;
    }

    .header-title {
      color: var(--text-dark);
      font-size: clamp(1.5rem, 4vw, 2.2rem);
      margin: 0.5rem 0 0 0;
    }

    footer {
      background-color: #212529;
      color: var(--text-light);
      margin-top: auto;
    }

    /* Responsive improvements */
    @media (min-width: 768px) {
      .header-content {
        flex-direction: row;
        justify-content: space-between;
        text-align: left;
      }
      
      .header-title {
        margin: 0;
      }
      
      .container {
        max-width: 90%;
      }
    }

    @media (max-width: 576px) {
      .card-header {
        padding: 0.75rem 1rem;
      }
      
      .list-group-item {
        padding: 0.5rem 1rem;
      }
      
      .container {
        padding-left: 10px;
        padding-right: 10px;
      }
    }

    /* Accessibility improvements */
    .sr-only {
      position: absolute;
      width: 1px;
      height: 1px;
      padding: 0;
      margin: -1px;
      overflow: hidden;
      clip: rect(0, 0, 0, 0);
      white-space: nowrap;
      border: 0;
    }

    a:focus {
      outline: 2px solid var(--primary-color);
      outline-offset: 2px;
    }

    /* Loading state for cards */
    .card.loading {
      opacity: 0.7;
      pointer-events: none;
    }