:root {
            --primary-color: #4361ee;
            --secondary-color: #3f37c9;
            --accent-color: #4895ef;
            --light-color: #f8f9fa;
            --dark-color: #212529;
            --success-color: #4cc9f0;
            --warning-color: #f72585;
            --border-radius: 12px;
            --box-shadow: 0 8px 20px rgba(0, 0, 0, 0.12);
            --transition: all 0.3s ease;
        }

        body {
            background: linear-gradient(135deg, #f5f7fa 0%, #e4e8f0 100%);
            padding-top: 20px;
            padding-bottom: 50px;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            color: #495057;
        }

        .app-container {
            max-width: 1200px;
            margin: 0 auto;
        }

        .header {
            text-align: center;
            margin-bottom: 30px;
            padding: 20px;
            background: white;
            border-radius: var(--border-radius);
            box-shadow: var(--box-shadow);
        }

        .app-title {
            color: var(--primary-color);
            font-weight: 700;
            margin-bottom: 5px;
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 12px;
        }

        .app-subtitle {
            color: #6c757d;
            font-size: 1.1rem;
        }

        .card {
            border: none;
            border-radius: var(--border-radius);
            box-shadow: var(--box-shadow);
            margin-bottom: 24px;
            transition: var(--transition);
        }

        .card:hover {
            transform: translateY(-5px);
            box-shadow: 0 12px 30px rgba(0, 0, 0, 0.15);
        }

        .card-header {
            background: linear-gradient(to right, var(--primary-color), var(--secondary-color));
            color: white;
            font-weight: 600;
            border-radius: var(--border-radius) var(--border-radius) 0 0 !important;
            padding: 15px 20px;
            display: flex;
            align-items: center;
            gap: 10px;
        }

        .card-body {
            padding: 25px;
        }

        .form-label {
            font-weight: 600;
            color: #495057;
            margin-bottom: 8px;
        }

        .required-label:after {
            content: " *";
            color: var(--warning-color);
        }

        .form-control, .form-select {
            border-radius: 8px;
            padding: 12px 15px;
            border: 1px solid #dee2e6;
            transition: var(--transition);
        }

        .form-control:focus, .form-select:focus {
            border-color: var(--accent-color);
            box-shadow: 0 0 0 0.25rem rgba(67, 97, 238, 0.15);
        }

        .form-switch .form-check-input {
            width: 48px;
            height: 24px;
            margin-right: 10px;
        }

        .form-switch .form-check-input:checked {
            background-color: var(--primary-color);
            border-color: var(--primary-color);
        }

        .test-case {
            background-color: #f8f9fa;
            border-radius: 10px;
            padding: 20px;
            margin-bottom: 20px;
            border-left: 4px solid var(--accent-color);
            transition: var(--transition);
        }

        .test-case:hover {
            background-color: #e9ecef;
        }

        .test-case-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 15px;
        }

        .test-case-title {
            font-weight: 600;
            color: var(--primary-color);
            display: flex;
            align-items: center;
            gap: 8px;
        }

        .btn {
            border-radius: 8px;
            padding: 10px 20px;
            font-weight: 600;
            transition: var(--transition);
            display: flex;
            align-items: center;
            gap: 8px;
        }

        .btn-primary {
            background: linear-gradient(to right, var(--primary-color), var(--accent-color));
            border: none;
        }

        .btn-primary:hover {
            background: linear-gradient(to right, var(--secondary-color), var(--primary-color));
            transform: translateY(-2px);
        }

        .btn-success {
            background: linear-gradient(to right, #2ecc71, #27ae60);
            border: none;
        }

        .btn-danger {
            background: linear-gradient(to right, #e74c3c, #c0392b);
            border: none;
        }

        .btn-outline-secondary {
            border: 1px solid #dee2e6;
        }

        .preview-area {
            background-color: #2d3748;
            color: #e2e8f0;
            border-radius: 10px;
            padding: 20px;
            font-family: 'Fira Code', 'Monaco', 'Cascadia Code', monospace;
            white-space: pre-wrap;
            height: 350px;
            overflow-y: auto;
            font-size: 14px;
            line-height: 1.5;
        }

        .json-key {
            color: #ff79c6;
        }

        .json-string {
            color: #50fa7b;
        }

        .json-number {
            color: #bd93f9;
        }

        .json-boolean {
            color: #ffb86c;
        }

        .action-buttons {
            display: flex;
            gap: 12px;
            flex-wrap: wrap;
        }

        .footer {
            text-align: center;
            margin-top: 40px;
            padding: 20px;
            color: #6c757d;
            font-size: 0.9rem;
        }

        .badge {
            padding: 8px 12px;
            border-radius: 20px;
            font-weight: 600;
        }

        .badge-primary {
            background-color: var(--primary-color);
        }

        .badge-success {
            background-color: var(--success-color);
        }
        @media (max-width: 768px) {
            .card-body {
                padding: 15px;
            }
            
            .action-buttons {
                flex-direction: column;
            }
            
            .btn {
                width: 100%;
            }
        }
        .preview-area::-webkit-scrollbar {
            width: 8px;
        }

        .preview-area::-webkit-scrollbar-track {
            background: #1a202c;
            border-radius: 4px;
        }

        .preview-area::-webkit-scrollbar-thumb {
            background: var(--accent-color);
            border-radius: 4px;
        }

        .preview-area::-webkit-scrollbar-thumb:hover {
            background: var(--primary-color);
        }

        @keyframes fadeIn {
            from { opacity: 0; transform: translateY(10px); }
            to { opacity: 1; transform: translateY(0); }
        }

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

        .config-tag {
            display: inline-block;
            background: #e9ecef;
            padding: 4px 10px;
            border-radius: 20px;
            font-size: 0.8rem;
            margin-right: 8px;
            margin-bottom: 8px;
            color: #495057;
        }
        
        .preview-card {
            height: 100%;
        }
        
        .preview-container {
            display: flex;
            flex-direction: column;
            height: 100%;
        }