:root {
            --primary: #2c3e50;
            --primary-dark: #1a252f;
            --secondary: #3498db;
            --accent: #9b59b6;
            --success: #27ae60;
            --warning: #f39c12;
            --danger: #e74c3c;
            --info: #1abc9c;
            --dark: #2c3e50;
            --light: #ecf0f1;
            --gray: #7f8c8d;
            --light-gray: #bdc3c7;
            --border-radius: 20px;
            --shadow: 0 15px 40px rgba(0, 0, 0, 0.12);
            --gradient: linear-gradient(135deg, #2c3e50, #3498db);
            --premium-gradient: linear-gradient(135deg, #f39c12, #e74c3c);
            --glass-bg: rgba(255, 255, 255, 0.98);
        }
        
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Segoe UI', 'Roboto', -apple-system, sans-serif;
            max-width: 100%;
        }
        
        html, body {
            overflow-x: hidden;
            min-height: 100vh;
            background: linear-gradient(135deg, #f8fafc 0%, #f1f5f9 100%);
            color: var(--dark);
        }
        
        .container {
            max-width: 1600px;
            margin: 0 auto;
            padding: 0 20px;
        }
        
        /* Professional Header */
        .professional-header {
            background: var(--glass-bg);
            backdrop-filter: blur(10px);
            color: var(--dark);
            padding: 40px 50px;
            border-radius: var(--border-radius);
            margin: 35px auto;
            box-shadow: var(--shadow);
            position: relative;
            overflow: hidden;
            border: 1px solid rgba(255, 255, 255, 0.3);
        }
        
        .professional-header::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            height: 6px;
            background: var(--gradient);
        }
        
        .header-content {
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex-wrap: wrap;
            gap: 30px;
        }
        
        .logo-section {
            display: flex;
            align-items: center;
            gap: 25px;
        }
        
        .logo-icon {
            width: 75px;
            height: 75px;
            background: var(--gradient);
            border-radius: 20px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 36px;
            color: white;
            box-shadow: 0 10px 30px rgba(44, 62, 80, 0.2);
        }
        
        .logo-text h1 {
            font-size: 3rem;
            font-weight: 900;
            background: var(--gradient);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
            line-height: 1.1;
        }
        
        .premium-tag {
            background: var(--premium-gradient);
            color: white;
            padding: 12px 28px;
            border-radius: 30px;
            font-size: 1.1rem;
            font-weight: 800;
            display: inline-block;
            margin-top: 15px;
            box-shadow: 0 8px 25px rgba(243, 156, 18, 0.3);
            letter-spacing: 1px;
        }
        
        .header-stats {
            display: grid;
            grid-template-columns: repeat(3, auto);
            gap: 35px;
            align-items: center;
        }
        
        .stat-badge {
            text-align: center;
            padding: 20px;
            background: rgba(52, 152, 219, 0.08);
            border-radius: 18px;
            min-width: 140px;
            border: 2px solid rgba(52, 152, 219, 0.1);
        }
        
        .stat-value {
            font-size: 2.5rem;
            font-weight: 900;
            color: var(--secondary);
            margin-bottom: 8px;
        }
        
        .stat-label {
            font-size: 1rem;
            font-weight: 700;
            color: var(--dark);
            text-transform: uppercase;
            letter-spacing: 1.5px;
        }
        
        /* Main Layout */
        .main-layout {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 40px;
            margin: 50px 0;
        }
        
        /* Calculator Card */
        .calculator-card {
            background: var(--glass-bg);
            backdrop-filter: blur(10px);
            border-radius: var(--border-radius);
            box-shadow: var(--shadow);
            padding: 45px;
            border: 1px solid rgba(255, 255, 255, 0.3);
            position: relative;
            overflow: hidden;
        }
        
        .calculator-card::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            height: 6px;
            background: var(--gradient);
        }
        
        .card-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 40px;
            padding-bottom: 25px;
            border-bottom: 3px solid rgba(44, 62, 80, 0.1);
        }
        
        .card-title {
            display: flex;
            align-items: center;
            gap: 20px;
            font-size: 2rem;
            font-weight: 800;
            color: var(--dark);
        }
        
        .card-title i {
            color: white;
            background: var(--gradient);
            width: 60px;
            height: 60px;
            border-radius: 18px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 1.8rem;
        }
        
        /* Calculator Form */
        .calculator-form {
            display: grid;
            gap: 30px;
        }
        
        .form-group {
            margin-bottom: 15px;
        }
        
        .form-label {
            display: flex;
            align-items: center;
            gap: 15px;
            margin-bottom: 15px;
            font-size: 1.2rem;
            font-weight: 700;
            color: var(--dark);
        }
        
        .form-label i {
            color: var(--secondary);
            background: rgba(52, 152, 219, 0.1);
            width: 45px;
            height: 45px;
            border-radius: 12px;
            display: flex;
            align-items: center;
            justify-content: center;
        }
        
        .form-input {
            width: 100%;
            padding: 20px 25px;
            font-size: 1.1rem;
            font-weight: 600;
            border: 3px solid rgba(44, 62, 80, 0.1);
            border-radius: 15px;
            background: white;
            color: var(--dark);
            transition: all 0.3s ease;
        }
        
        .form-input:focus {
            outline: none;
            border-color: var(--secondary);
            box-shadow: 0 0 0 4px rgba(52, 152, 219, 0.1);
        }
        
        .form-select {
            width: 100%;
            padding: 20px 25px;
            font-size: 1.1rem;
            font-weight: 600;
            border: 3px solid rgba(44, 62, 80, 0.1);
            border-radius: 15px;
            background: white;
            color: var(--dark);
            cursor: pointer;
            transition: all 0.3s ease;
            appearance: none;
            background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%232c3e50' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
            background-repeat: no-repeat;
            background-position: right 25px center;
            background-size: 20px;
        }
        
        .form-select:focus {
            outline: none;
            border-color: var(--secondary);
            box-shadow: 0 0 0 4px rgba(52, 152, 219, 0.1);
        }
        
        /* GST Rate Cards */
        .gst-rates-grid {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 15px;
            margin: 25px 0;
        }
        
        .rate-card {
            padding: 20px;
            border: 3px solid rgba(44, 62, 80, 0.1);
            border-radius: 15px;
            text-align: center;
            cursor: pointer;
            transition: all 0.3s ease;
            background: white;
        }
        
        .rate-card:hover {
            transform: translateY(-5px);
            border-color: var(--secondary);
            box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
        }
        
        .rate-card.active {
            background: var(--gradient);
            color: white;
            border-color: var(--secondary);
            transform: scale(1.05);
        }
        
        .rate-value {
            font-size: 1.8rem;
            font-weight: 900;
            margin-bottom: 5px;
        }
        
        .rate-label {
            font-size: 0.9rem;
            font-weight: 600;
            opacity: 0.9;
        }
        
        /* Action Buttons */
        .action-buttons {
            display: grid;
            grid-template-columns: repeat(2, 1fr);
            gap: 20px;
            margin-top: 35px;
        }
        
        .premium-btn {
            background: var(--gradient);
            color: white;
            border: none;
            padding: 25px 40px;
            border-radius: var(--border-radius);
            font-size: 1.3rem;
            font-weight: 800;
            cursor: pointer;
            transition: all 0.3s ease;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            gap: 15px;
            box-shadow: 0 10px 30px rgba(44, 62, 80, 0.2);
            position: relative;
            overflow: hidden;
        }
        
        .premium-btn::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
            transition: left 0.6s;
        }
        
        .premium-btn:hover::before {
            left: 100%;
        }
        
        .premium-btn:hover:not(:disabled) {
            transform: translateY(-5px);
            box-shadow: 0 20px 40px rgba(44, 62, 80, 0.3);
        }
        
        .premium-btn:active:not(:disabled) {
            transform: translateY(-2px);
        }
        
        .premium-btn:disabled {
            opacity: 0.6;
            cursor: not-allowed;
            transform: none !important;
        }
        
        .btn-success {
            background: linear-gradient(135deg, var(--success), #2ecc71);
        }
        
        .btn-warning {
            background: linear-gradient(135deg, var(--warning), #f1c40f);
        }
        
        .btn-danger {
            background: linear-gradient(135deg, var(--danger), #c0392b);
        }
        
        .btn-accent {
            background: var(--premium-gradient);
        }
        
        .btn-info {
            background: linear-gradient(135deg, var(--info), #16a085);
        }
        
        /* Results Card */
        .results-card {
            background: var(--glass-bg);
            backdrop-filter: blur(10px);
            border-radius: var(--border-radius);
            box-shadow: var(--shadow);
            padding: 45px;
            border: 1px solid rgba(255, 255, 255, 0.3);
        }
        
        .results-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 40px;
            padding-bottom: 25px;
            border-bottom: 3px solid rgba(44, 62, 80, 0.1);
        }
        
        /* Results Display */
        .results-display {
            display: grid;
            gap: 25px;
        }
        
        .result-item {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 25px;
            background: linear-gradient(135deg, #f8fafc, #f1f5f9);
            border-radius: 15px;
            border-left: 6px solid var(--secondary);
            transition: all 0.3s ease;
        }
        
        .result-item:hover {
            transform: translateX(10px);
            box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
        }
        
        .result-label {
            font-size: 1.1rem;
            font-weight: 700;
            color: var(--dark);
            display: flex;
            align-items: center;
            gap: 12px;
        }
        
        .result-label i {
            color: var(--secondary);
            font-size: 1.3rem;
        }
        
        .result-value {
            font-size: 1.8rem;
            font-weight: 900;
            color: var(--secondary);
        }
        
        .result-value.total {
            font-size: 2.5rem;
            color: var(--success);
        }
        
        /* GST Breakdown */
        .gst-breakdown {
            background: linear-gradient(135deg, rgba(52, 152, 219, 0.05), rgba(155, 89, 182, 0.05));
            padding: 30px;
            border-radius: 20px;
            margin: 30px 0;
            border: 2px solid rgba(52, 152, 219, 0.1);
        }
        
        .breakdown-grid {
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            gap: 20px;
            text-align: center;
        }
        
        .breakdown-item {
            padding: 20px;
            background: white;
            border-radius: 15px;
            border: 2px solid rgba(44, 62, 80, 0.1);
        }
        
        .breakdown-label {
            font-size: 0.9rem;
            color: var(--gray);
            font-weight: 600;
            margin-bottom: 10px;
        }
        
        .breakdown-value {
            font-size: 1.5rem;
            font-weight: 900;
            color: var(--secondary);
        }
        
        .breakdown-value.sgst {
            color: var(--accent);
        }
        
        .breakdown-value.cgst {
            color: var(--success);
        }
        
        .breakdown-value.igst {
            color: var(--warning);
        }
        
        /* Invoice Generator */
        .invoice-section {
            margin-top: 40px;
            padding: 35px;
            background: linear-gradient(135deg, #f8fafc, #f1f5f9);
            border-radius: 20px;
            border: 2px solid rgba(44, 62, 80, 0.1);
        }
        
        .invoice-preview {
            background: white;
            padding: 30px;
            border-radius: 15px;
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
            margin-top: 25px;
            font-family: 'Courier New', monospace;
        }
        
        /* History Section */
        .history-section {
            margin-top: 40px;
        }
        
        .history-list {
            max-height: 350px;
            overflow-y: auto;
            margin-top: 25px;
        }
        
        .history-item {
            display: flex;
            align-items: center;
            gap: 20px;
            padding: 20px;
            background: white;
            border-radius: 15px;
            margin-bottom: 15px;
            border: 2px solid rgba(44, 62, 80, 0.1);
            transition: all 0.3s ease;
        }
        
        .history-item:hover {
            transform: translateX(10px);
            border-color: var(--secondary);
        }
        
        .history-icon {
            width: 60px;
            height: 60px;
            background: var(--gradient);
            border-radius: 15px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 1.5rem;
            color: white;
        }
        
        .history-info {
            flex: 1;
        }
        
        .history-title {
            font-weight: 700;
            margin-bottom: 5px;
            color: var(--dark);
        }
        
        .history-details {
            display: flex;
            gap: 20px;
            font-size: 0.9rem;
            color: var(--gray);
        }
        
        /* Premium Features Section */
        .premium-features {
            background: linear-gradient(135deg, rgba(44, 62, 80, 0.9), rgba(26, 37, 47, 0.9));
            color: white;
            padding: 60px 50px;
            border-radius: var(--border-radius);
            margin: 60px 0;
            position: relative;
            overflow: hidden;
        }
        
        .premium-features::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            height: 6px;
            background: var(--premium-gradient);
        }
        
        .features-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
            gap: 35px;
            margin-top: 50px;
        }
        
        .feature-card {
            background: rgba(255, 255, 255, 0.05);
            padding: 40px 35px;
            border-radius: 25px;
            text-align: center;
            transition: all 0.4s ease;
            border: 2px solid rgba(255, 255, 255, 0.1);
            position: relative;
            backdrop-filter: blur(10px);
        }
        
        .feature-card:hover {
            transform: translateY(-15px) scale(1.02);
            background: rgba(255, 255, 255, 0.1);
            border-color: var(--premium-gradient);
            box-shadow: 0 25px 50px rgba(0, 0, 0, 0.2);
        }
        
        .feature-icon {
            width: 85px;
            height: 85px;
            background: var(--premium-gradient);
            border-radius: 20px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 2.2rem;
            color: white;
            margin: 0 auto 30px;
            box-shadow: 0 15px 35px rgba(243, 156, 18, 0.3);
        }
        
        /* HSN Code Search */
        .hsn-search {
            margin: 30px 0;
            padding: 30px;
            background: linear-gradient(135deg, rgba(52, 152, 219, 0.05), rgba(155, 89, 182, 0.05));
            border-radius: 20px;
            border: 2px solid rgba(52, 152, 219, 0.1);
        }
        
        /* Tax Slabs Section */
        .tax-slabs {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 20px;
            margin: 30px 0;
        }
        
        .slab-card {
            padding: 25px;
            background: white;
            border-radius: 15px;
            text-align: center;
            border: 3px solid rgba(44, 62, 80, 0.1);
            transition: all 0.3s ease;
        }
        
        .slab-card:hover {
            transform: translateY(-8px);
            border-color: var(--secondary);
            box-shadow: 0 15px 35px rgba(0, 0, 0, 0.1);
        }
        
        .slab-rate {
            font-size: 2.2rem;
            font-weight: 900;
            color: var(--secondary);
            margin-bottom: 10px;
        }
        
        /* Notification */
        .notification {
            position: fixed;
            bottom: 50px;
            right: 50px;
            padding: 25px 35px;
            background: var(--dark);
            color: white;
            border-radius: 20px;
            box-shadow: 0 20px 50px rgba(0, 0, 0, 0.25);
            display: none;
            z-index: 1000;
            animation: slideIn 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
            max-width: 500px;
            border-left: 8px solid var(--secondary);
        }
        
        @keyframes slideIn {
            from {
                opacity: 0;
                transform: translateX(150px) scale(0.9);
            }
            to {
                opacity: 1;
                transform: translateX(0) scale(1);
            }
        }
        
        .notification.show {
            display: flex;
            align-items: center;
            gap: 20px;
        }
        
        /* Loader */
        .loader {
            display: inline-block;
            width: 28px;
            height: 28px;
            border: 4px solid rgba(255, 255, 255, 0.3);
            border-radius: 50%;
            border-top-color: white;
            animation: spin 1s linear infinite;
        }
        
        @keyframes spin {
            to { transform: rotate(360deg); }
        }
        
        /* Mobile Responsive */
        @media (max-width: 1200px) {
            .main-layout {
                grid-template-columns: 1fr;
                gap: 40px;
            }
            
            .gst-rates-grid {
                grid-template-columns: repeat(2, 1fr);
            }
            
            .breakdown-grid {
                grid-template-columns: repeat(2, 1fr);
            }
        }
        
        @media (max-width: 992px) {
            .professional-header {
                padding: 30px 35px;
            }
            
            .logo-text h1 {
                font-size: 2.5rem;
            }
            
            .header-stats {
                grid-template-columns: repeat(3, auto);
                gap: 25px;
            }
            
            .stat-badge {
                min-width: 120px;
                padding: 15px;
            }
            
            .calculator-card, .results-card {
                padding: 35px 30px;
            }
            
            .features-grid {
                grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
            }
        }
        
        @media (max-width: 768px) {
            body {
                padding: 15px 10px;
            }
            
            .container {
                padding: 0 15px;
            }
            
            .professional-header {
                padding: 25px 30px;
                margin: 25px 0;
            }
            
            .header-content {
                flex-direction: column;
                text-align: center;
                gap: 35px;
            }
            
            .logo-section {
                flex-direction: column;
            }
            
            .header-stats {
                grid-template-columns: repeat(3, auto);
                justify-content: center;
            }
            
            .action-buttons {
                grid-template-columns: 1fr;
            }
            
            .gst-rates-grid {
                grid-template-columns: repeat(2, 1fr);
            }
            
            .breakdown-grid {
                grid-template-columns: 1fr;
            }
            
            .tax-slabs {
                grid-template-columns: repeat(2, 1fr);
            }
            
            .premium-btn {
                padding: 20px 30px;
                width: 100%;
                justify-content: center;
            }
            
            .notification {
                bottom: 30px;
                right: 30px;
                left: 30px;
                max-width: calc(100% - 60px);
            }
            
            .premium-features {
                padding: 40px 30px;
            }
            
            .feature-card {
                padding: 30px 25px;
            }
        }
        
        @media (max-width: 576px) {
            .container {
                padding: 0 10px;
            }
            
            .logo-text h1 {
                font-size: 2.2rem;
            }
            
            .premium-tag {
                padding: 10px 25px;
                font-size: 1rem;
            }
            
            .header-stats {
                grid-template-columns: repeat(3, auto);
                gap: 15px;
            }
            
            .stat-badge {
                min-width: 100px;
                padding: 12px 15px;
            }
            
            .stat-value {
                font-size: 2rem;
            }
            
            .calculator-card, .results-card {
                padding: 30px 20px;
            }
            
            .card-title {
                font-size: 1.6rem;
            }
            
            .gst-rates-grid {
                grid-template-columns: 1fr;
            }
            
            .tax-slabs {
                grid-template-columns: 1fr;
            }
            
            .result-value {
                font-size: 1.5rem;
            }
            
            .result-value.total {
                font-size: 2rem;
            }
            
            .feature-card {
                padding: 25px 20px;
            }
            
            .feature-icon {
                width: 70px;
                height: 70px;
                font-size: 1.8rem;
            }
        }
        
        /* Utility Classes */
        .text-center {
            text-align: center;
        }
        
        .mt-40 {
            margin-top: 40px;
        }
        
        .mb-40 {
            margin-bottom: 40px;
        }
        
        .hidden {
            display: none !important;
        }
        
        .flex-center {
            display: flex;
            align-items: center;
            justify-content: center;
        }
        
        .space-between {
            display: flex;
            justify-content: space-between;
            align-items: center;
        }
        
        /* Chart Styles */
        .chart-container {
            height: 300px;
            margin: 30px 0;
            position: relative;
        }
        
        /* Toggle Switch */
        .toggle-switch {
            position: relative;
            display: inline-block;
            width: 70px;
            height: 34px;
        }
        
        .toggle-switch input {
            opacity: 0;
            width: 0;
            height: 0;
        }
        
        .toggle-slider {
            position: absolute;
            cursor: pointer;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background-color: #ccc;
            transition: .4s;
            border-radius: 34px;
        }
        
        .toggle-slider:before {
            position: absolute;
            content: "";
            height: 26px;
            width: 26px;
            left: 4px;
            bottom: 4px;
            background-color: white;
            transition: .4s;
            border-radius: 50%;
        }
        
        input:checked + .toggle-slider {
            background-color: var(--success);
        }
        
        input:checked + .toggle-slider:before {
            transform: translateX(36px);
        }
        
        /* Tooltip */
        .tooltip {
            position: relative;
            display: inline-block;
            cursor: help;
        }
        
        .tooltip .tooltip-text {
            visibility: hidden;
            width: 250px;
            background-color: var(--dark);
            color: white;
            text-align: center;
            border-radius: 10px;
            padding: 15px;
            position: absolute;
            z-index: 1;
            bottom: 125%;
            left: 50%;
            margin-left: -125px;
            opacity: 0;
            transition: opacity 0.3s;
            font-size: 0.9rem;
            font-weight: 400;
        }
        
        .tooltip:hover .tooltip-text {
            visibility: visible;
            opacity: 1;
        }