:root {
      --primary-color: #2563eb;
      --secondary-color: #64748b;
      --success-color: #10b981;
      --background-color: #f8fafc;
      --card-bg: #ffffff;
      --text-primary: #1e293b;
      --text-secondary: #64748b;
      --border-color: #e2e8f0;
      --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
      --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    }

    body {
      background-color: var(--background-color);
      font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
      color: var(--text-primary);
    }

 
    .sidebar {
      background: linear-gradient(135deg, var(--card-bg) 0%, #f1f5f9 100%);
      border-right: 1px solid var(--border-color);
      min-height: 100vh;
      position: sticky;
      top: 0;
    }

    .logo {
      max-height: 60px;
      width: auto;
      transition: transform 0.2s ease;
    }

    .logo:hover {
      transform: scale(1.02);
    }

    .sidebar .nav-link {
      color: var(--text-secondary);
      font-weight: 500;
      padding: 0.75rem 1.5rem;
      margin: 0.25rem 0;
      border-radius: 0.5rem;
      transition: all 0.2s ease;
      position: relative;
    }

    .sidebar .nav-link:hover {
      background-color: rgba(37, 99, 235, 0.1);
      color: var(--primary-color);
      transform: translateX(4px);
    }

    .sidebar .nav-link.active {
      background-color: var(--primary-color);
      color: white;
      box-shadow: var(--shadow);
    }

    .sidebar .nav-link.active::before {
      content: '';
      position: absolute;
      left: 0;
      top: 0;
      height: 100%;
      width: 3px;
      background-color: white;
      border-radius: 0 2px 2px 0;
    }

    
    .navbar {
      backdrop-filter: blur(10px);
      background-color: rgba(255, 255, 255, 0.95) !important;
    }

    
    .main-content {
      padding: 2rem;
    }

    
    .page-header {
      background: linear-gradient(135deg, var(--primary-color) 0%, #3b82f6 100%);
      color: white;
      border-radius: 1rem;
      padding: 2rem;
      margin-bottom: 2rem;
      box-shadow: var(--shadow-lg);
    }

    .page-header h3 {
      font-size: 2rem;
      font-weight: 700;
      margin: 0;
    }

    .page-header .subtitle {
      opacity: 0.9;
      font-size: 1.1rem;
      margin-top: 0.5rem;
    }

    
    .stats-card {
      background: var(--card-bg);
      border: none;
      border-radius: 1rem;
      box-shadow: var(--shadow);
      transition: all 0.3s ease;
      overflow: hidden;
      position: relative;
    }

    .stats-card::before {
      content: '';
      position: absolute;
      top: 0;
      left: 0;
      right: 0;
      height: 4px;
      background: linear-gradient(90deg, var(--primary-color), #3b82f6);
    }

    .stats-card:hover {
      transform: translateY(-2px);
      box-shadow: var(--shadow-lg);
    }

    .stats-card .card-body {
      padding: 1.5rem;
    }

    .stats-icon {
      width: 50px;
      height: 50px;
      border-radius: 0.75rem;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 1.5rem;
      margin-bottom: 1rem;
    }

    .sales-icon {
      background: linear-gradient(135deg, #10b981, #059669);
      color: white;
    }

    .invoice-icon {
      background: linear-gradient(135deg, #3b82f6, #2563eb);
      color: white;
    }

    .stats-value {
      font-size: 2rem;
      font-weight: 700;
      color: var(--text-primary);
      margin: 0;
      line-height: 1;
    }

    .stats-label {
      color: var(--text-secondary);
      font-size: 0.875rem;
      font-weight: 500;
      margin-top: 0.5rem;
    }

    
    .recent-invoices-card {
      background: var(--card-bg);
      border: none;
      border-radius: 1rem;
      box-shadow: var(--shadow);
      overflow: hidden;
    }

    .card-header-custom {
      background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
      border-bottom: 1px solid var(--border-color);
      padding: 1.5rem;
    }

    .card-header-custom h5 {
      margin: 0;
      font-weight: 600;
      color: var(--text-primary);
    }

    .recent-invoice-item {
      padding: 1rem 1.5rem;
      border-bottom: 1px solid var(--border-color);
      transition: all 0.2s ease;
      cursor: pointer;
    }

    .recent-invoice-item:last-child {
      border-bottom: none;
    }

    .recent-invoice-item:hover {
      background-color: rgba(37, 99, 235, 0.03);
      transform: translateX(4px);
    }

    .invoice-id {
      font-weight: 600;
      color: var(--primary-color);
      font-size: 0.95rem;
    }

    .customer-name {
      color: var(--text-secondary);
      font-size: 0.875rem;
      margin-top: 0.25rem;
    }

    .invoice-amount {
      font-weight: 600;
      color: var(--success-color);
      font-size: 1.1rem;
    }

   
    .btn-primary {
      background: linear-gradient(135deg, var(--primary-color), #3b82f6);
      border: none;
      border-radius: 0.5rem;
      font-weight: 500;
      padding: 0.75rem 1.5rem;
      transition: all 0.2s ease;
      box-shadow: var(--shadow);
    }

    .btn-primary:hover {
      transform: translateY(-1px);
      box-shadow: var(--shadow-lg);
      background: linear-gradient(135deg, #1d4ed8, var(--primary-color));
    }

    .btn-danger {
      background: linear-gradient(135deg, #ef4444, #dc2626);
      border: none;
      border-radius: 0.5rem;
      font-weight: 500;
      transition: all 0.2s ease;
      box-shadow: var(--shadow);
    }

    .btn-danger:hover {
      transform: translateY(-1px);
      box-shadow: var(--shadow-lg);
      background: linear-gradient(135deg, #dc2626, #b91c1c);
    }

    
    .empty-state {
      text-align: center;
      padding: 3rem 1rem;
      color: var(--text-secondary);
    }

    .empty-state i {
      font-size: 3rem;
      margin-bottom: 1rem;
      opacity: 0.5;
    }

    
    @media (max-width: 768px) {
      .main-content {
        padding: 1rem;
      }

      .page-header {
        padding: 1.5rem;
        text-align: center;
      }

      .page-header h3 {
        font-size: 1.5rem;
      }

      .stats-card {
        margin-bottom: 1rem;
      }
    }

    
    .fade-in {
      animation: fadeIn 0.5s ease-in;
    }

    @keyframes fadeIn {
      from { opacity: 0; transform: translateY(20px); }
      to { opacity: 1; transform: translateY(0); }
    }