:root {
            --primary: #4361ee;
            --primary-light: #5a75f8;
            --primary-dark: #3a56d4;
            --secondary: #6c63ff;
            --light: #f8f9fa;
            --light-bg: #f5f7ff;
            --dark: #2b2d42;
            --light-text: #6c757d;
            --border: #e0e7ff;
            --success: #4cc9f0;
            --shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
            --radius: 12px;
            --transition: all 0.3s ease;
        }
        
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
        }
        
        body {
            background: linear-gradient(135deg, #f5f7ff 0%, #e6e9ff 100%);
            color: var(--dark);
            line-height: 1.6;
            padding: 20px;
            min-height: 100vh;
        }
        
        .container {
            max-width: 1400px;
            margin: 0 auto;
        }
        
        header {
            background: white;
            padding: 20px 30px;
            border-radius: var(--radius);
            margin-bottom: 30px;
            box-shadow: var(--shadow);
            display: flex;
            justify-content: space-between;
            align-items: center;
            position: sticky;
            top: 20px;
            z-index: 100;
            border: 1px solid var(--border);
        }
        
        .logo-container {
            display: flex;
            align-items: center;
            gap: 15px;
        }
        
        .logo {
            width: 50px;
            height: 50px;
            background: linear-gradient(135deg, var(--primary), var(--secondary));
            border-radius: 10px;
            display: flex;
            align-items: center;
            justify-content: center;
            color: white;
            font-weight: bold;
            font-size: 22px;
        }
        
        .app-title {
            font-size: 24px;
            font-weight: 700;
            color: var(--dark);
        }
        
        .app-subtitle {
            font-size: 14px;
            color: var(--light-text);
            margin-top: 4px;
        }
        
        .app-container {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 30px;
            margin-bottom: 50px;
        }
        
        @media (max-width: 1100px) {
            .app-container {
                grid-template-columns: 1fr;
            }
        }
        
        .panel {
            background: white;
            border-radius: var(--radius);
            padding: 30px;
            box-shadow: var(--shadow);
            border: 1px solid var(--border);
            transition: var(--transition);
        }
        
        .panel:hover {
            box-shadow: 0 10px 25px rgba(0, 0, 0, 0.08);
        }
        
        .section-title {
            font-size: 1.4rem;
            margin-bottom: 25px;
            padding-bottom: 15px;
            border-bottom: 2px solid var(--border);
            color: var(--dark);
            font-weight: 600;
            display: flex;
            align-items: center;
            gap: 10px;
        }
        
        .form-group {
            margin-bottom: 25px;
        }
        
        label {
            display: block;
            margin-bottom: 8px;
            font-weight: 500;
            color: var(--dark);
            font-size: 15px;
        }
        
        input, select, textarea {
            width: 100%;
            padding: 14px;
            border: 1px solid var(--border);
            border-radius: 8px;
            font-size: 1rem;
            background: white;
            transition: var(--transition);
        }
        
        input:focus, select:focus, textarea:focus {
            outline: none;
            border-color: var(--primary);
            box-shadow: 0 0 0 3px rgba(67, 97, 238, 0.15);
        }
        
        .upload-area {
            border: 2px dashed var(--border);
            border-radius: 8px;
            padding: 30px 20px;
            text-align: center;
            margin-bottom: 20px;
            cursor: pointer;
            transition: var(--transition);
            background: var(--light-bg);
        }
        
        .upload-area:hover {
            border-color: var(--primary);
            background: rgba(67, 97, 238, 0.03);
        }
        
        .details-grid {
            display: grid;
            grid-template-columns: repeat(2, 1fr);
            gap: 15px;
        }
        
        .address-section {
            display: grid;
            grid-template-columns: repeat(2, 1fr);
            gap: 20px;
            margin: 25px 0;
        }
        
        .items-table {
            width: 100%;
            border-collapse: collapse;
            margin: 20px 0;
            border-radius: 8px;
            overflow: hidden;
        }
        
        .items-table th {
            background-color: var(--primary);
            color: white;
            text-align: left;
            padding: 15px;
            font-weight: 500;
        }
        
        .items-table td {
            padding: 15px;
            border-bottom: 1px solid var(--border);
        }
        
        .items-table input {
            width: 100%;
            padding: 10px;
            border: 1px solid #eaefff;
            border-radius: 6px;
            background: #fafbff;
        }
        
        .btn-container {
            display: flex;
            gap: 12px;
            margin-top: 15px;
            flex-wrap: wrap;
        }
        
        .btn {
            padding: 14px 24px;
            border-radius: 8px;
            cursor: pointer;
            transition: var(--transition);
            border: none;
            font-size: 1rem;
            display: flex;
            align-items: center;
            gap: 8px;
            font-weight: 500;
        }
        
        .btn-primary {
            background: linear-gradient(135deg, var(--primary), var(--secondary));
            color: white;
            box-shadow: 0 4px 12px rgba(67, 97, 238, 0.25);
        }
        
        .btn-primary:hover {
            transform: translateY(-2px);
            box-shadow: 0 6px 15px rgba(67, 97, 238, 0.35);
            background: linear-gradient(135deg, var(--primary-light), #7a72ff);
        }
        
        .btn-outline {
            background-color: transparent;
            border: 1px solid var(--border);
            color: var(--dark);
        }
        
        .btn-outline:hover {
            background-color: rgba(67, 97, 238, 0.05);
            border-color: var(--primary);
        }
        
        .btn-danger {
            background-color: #ff6b6b;
            color: white;
        }
        
        .btn-danger:hover {
            background-color: #ff5252;
        }
        
        .totals {
            background-color: var(--light-bg);
            padding: 20px;
            border-radius: 8px;
            margin: 25px 0;
            border: 1px solid var(--border);
        }
        
        .total-row {
            display: flex;
            justify-content: space-between;
            margin-bottom: 12px;
            padding-bottom: 12px;
            border-bottom: 1px dashed var(--border);
        }
        
        .total-label {
            font-weight: 500;
        }
        
        .total-value {
            font-weight: 600;
        }
        
        .grand-total {
            font-size: 1.3rem;
            color: var(--primary);
            padding-top: 12px;
            margin-top: 8px;
            border-top: 2px solid var(--border);
        }
        
        .payment-options {
            display: flex;
            gap: 12px;
            flex-wrap: wrap;
            margin: 20px 0;
        }
        
        .payment-option {
            flex: 1;
            min-width: 130px;
            text-align: center;
            padding: 18px;
            border: 1px solid var(--border);
            border-radius: 8px;
            cursor: pointer;
            transition: var(--transition);
            background: white;
        }
        
        .payment-option:hover {
            transform: translateY(-3px);
            box-shadow: var(--shadow);
            border-color: var(--primary);
        }
        
        .payment-option.selected {
            border-color: var(--primary);
            background-color: rgba(67, 97, 238, 0.05);
            box-shadow: 0 4px 10px rgba(67, 97, 238, 0.1);
        }
        
        .invoice-preview-content {
            background: white;
            border: 1px solid var(--border);
            padding: 40px;
            min-height: 800px;
            border-radius: 12px;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.03);
        }
        
        .preview-logo {
            max-width: 180px;
            margin-bottom: 25px;
        }
        
        .preview-header {
            display: flex;
            justify-content: space-between;
            margin-bottom: 40px;
        }
        
        .preview-addresses {
            display: flex;
            justify-content: space-between;
            margin-bottom: 50px;
            gap: 30px;
        }
        
        .preview-address {
            flex: 1;
        }
        
        .preview-title {
            font-weight: 600;
            margin-bottom: 15px;
            color: var(--primary);
            font-size: 18px;
        }
        
        footer {
            text-align: center;
            margin-top: 40px;
            padding: 20px;
            color: var(--light-text);
            font-size: 14px;
        }
        
        .features-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 25px;
            margin: 50px 0;
        }
        
        .feature-card {
            background: white;
            border-radius: var(--radius);
            padding: 30px;
            box-shadow: var(--shadow);
            text-align: center;
            border: 1px solid var(--border);
            transition: var(--transition);
        }
        
        .feature-card:hover {
            transform: translateY(-5px);
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.08);
        }
        
        .currency-container {
            display: flex;
            gap: 12px;
        }
        
        .currency-container select {
            flex: 1;
        }
        
        .currency-container input {
            width: 80px;
        }
        
        .delete-item {
            color: #ff6b6b;
            cursor: pointer;
            font-weight: bold;
            font-size: 1.4rem;
            transition: var(--transition);
        }
        
        .delete-item:hover {
            color: #ff5252;
            transform: scale(1.1);
        }
        
        .preview-meta {
            background: var(--light-bg);
            padding: 15px 20px;
            border-radius: 8px;
            margin-bottom: 25px;
        }
        
        .preview-meta p {
            margin-bottom: 5px;
            display: flex;
            gap: 15px;
        }
        
        .preview-meta span:first-child {
            font-weight: 500;
            min-width: 120px;
            color: var(--light-text);
        }
        
        .custom-payment-details {
            display: none;
            margin-top: 15px;
        }
        
        .custom-payment-details.active {
            display: block;
        }
        
        /* Animation for smooth interactions */
        @keyframes fadeIn {
            from { opacity: 0; transform: translateY(10px); }
            to { opacity: 1; transform: translateY(0); }
        }
        
        .panel {
            animation: fadeIn 0.4s ease-out;
        }
        
        /* Loading spinner */
        .spinner {
            width: 40px;
            height: 40px;
            border: 4px solid rgba(67, 97, 238, 0.2);
            border-top: 4px solid var(--primary);
            border-radius: 50%;
            animation: spin 1s linear infinite;
            margin: 20px auto;
        }
        
        @keyframes spin {
            0% { transform: rotate(0deg); }
            100% { transform: rotate(360deg); }
        }
        
        /* Responsive adjustments */
        @media (max-width: 768px) {
            .details-grid, .address-section {
                grid-template-columns: 1fr;
            }
            
            .currency-container {
                flex-direction: column;
            }
            
            .currency-container input {
                width: 100%;
            }
            
            .preview-addresses {
                flex-direction: column;
            }
            
            .btn {
                width: 100%;
                justify-content: center;
            }
            
            header {
                flex-direction: column;
                gap: 20px;
            }
        }
        
        .status-indicator {
            display: inline-block;
            width: 12px;
            height: 12px;
            border-radius: 50%;
            margin-left: 10px;
            background: #4ade80;
        }
        
        .status-indicator.calculating {
            background: #f59e0b;
        }
        
        .btn-disabled {
            opacity: 0.7;
            cursor: not-allowed;
        }
        
        .payment-details-group {
            display: none;
            margin-top: 15px;
        }
        
        .payment-details-group.active {
            display: block;
        }