:root {
     --primary-color: #4e73df;
     --secondary-color: #f8f9fc;
     --accent-color: #2e59d9;
 }

 body {
     background-color: #f8f9fc;
     font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
 }

 .navbar-brand {
     font-weight: 700;
     font-size: 1.5rem;
 }

 .tagline {
     font-size: 0.9rem;
     color: #6c757d;
     margin-left: 10px;
 }

 .main-card {
     border-radius: 15px;
     box-shadow: 0 0.15rem 1.75rem 0 rgba(58, 59, 69, 0.15);
     border: none;
     margin-top: 30px;
     margin-bottom: 30px;
 }

 .card-header {
     background-color: var(--primary-color);
     color: white;
     border-radius: 15px 15px 0 0 !important;
     padding: 1.25rem 1.5rem;
     border-bottom: none;
 }

 .card-body {
     padding: 2rem;
 }

 .form-label {
     font-weight: 600;
 }

 .email-input-toggle {
     display: flex;
     gap: 20px;
     margin-bottom: 15px;
 }

 .email-input-toggle .btn-check:checked+.btn {
     background-color: var(--primary-color);
     color: white;
 }

 .logs-table {
     margin-top: 30px;
 }

 .status-sent {
     color: #1cc88a;
 }

 .status-failed {
     color: #e74a3b;
 }

 footer {
     background-color: white;
     padding: 20px 0;
     margin-top: 30px;
     box-shadow: 0 -0.15rem 0.5rem 0 rgba(58, 59, 69, 0.1);
 }

 /* Responsive adjustments */
 @media (max-width: 768px) {
     .card-body {
         padding: 1.5rem;
     }

     .email-input-toggle {
         flex-direction: column;
         gap: 10px;
     }
 }