:root {
            --primary: #2563eb;
            --primary-dark: #1d4ed8;
            --success: #059669;
            --success-dark: #047857;
            --danger: #ef4444;
            --danger-dark: #dc2626;
            --warning: #f59e0b;
            --warning-dark: #d97706;
            --purple: #7c3aed;
            --purple-dark: #6d28d9;
            --gray-100: #f9fafb;
            --gray-200: #f3f4f6;
            --gray-300: #e5e7eb;
            --gray-400: #d1d5db;
            --gray-500: #6b7280;
            --gray-700: #374151;
            --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
            --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.1);
        }
        
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        
        body {
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
            line-height: 1.6;
            color: var(--gray-700);
            background-color: #f0f7ff;
            padding: 20px;
        }
        
        .profit-calculator-container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 20px;
        }
        
        /* Header Styles */
        .calculator-header {
            text-align: center;
            margin-bottom: 40px;
        }
        
        .main-title {
            font-size: 2.5rem;
            font-weight: 700;
            color: var(--primary);
            margin-bottom: 20px;
            line-height: 1.2;
        }
        
        .description {
            font-size: 1.1rem;
            color: var(--gray-500);
            max-width: 800px;
            margin: 0 auto;
            line-height: 1.7;
        }
        
        /* Main Calculator Section */
        .calculator-main {
            background: #ffffff;
            border-radius: 16px;
            box-shadow: var(--shadow-lg);
            padding: 40px;
            margin-bottom: 40px;
            border: 1px solid var(--gray-300);
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 30px;
        }
        
        .input-section, .results-section {
            padding: 20px;
        }
        
        .section-title {
            font-size: 1.3rem;
            font-weight: 600;
            color: var(--gray-700);
            margin-bottom: 20px;
            padding-bottom: 10px;
            border-bottom: 2px solid var(--gray-300);
        }
        
        /* Input Form */
        .form-group {
            margin-bottom: 20px;
        }
        
        .form-label {
            display: block;
            margin-bottom: 8px;
            font-weight: 500;
            color: var(--gray-700);
        }
        
        .input-with-icon {
            position: relative;
        }
        
        .currency-icon {
            position: absolute;
            left: 12px;
            top: 50%;
            transform: translateY(-50%);
            color: var(--gray-500);
        }
        
        .form-input {
            width: 100%;
            padding: 14px 14px 14px 40px;
            border: 2px solid var(--gray-300);
            border-radius: 10px;
            font-size: 1rem;
            transition: all 0.3s ease;
        }
        
        .form-input:focus {
            border-color: var(--primary);
            outline: none;
            box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.2);
        }
        
        .calculate-btn {
            background: linear-gradient(135deg, var(--success), var(--success-dark));
            color: white;
            border: none;
            padding: 15px 30px;
            border-radius: 10px;
            font-size: 1.1rem;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            box-shadow: 0 4px 12px rgba(5, 150, 105, 0.3);
            width: 100%;
            margin-top: 10px;
        }
        
        .calculate-btn:hover {
            background: linear-gradient(135deg, var(--success-dark), #065f46);
            transform: translateY(-2px);
            box-shadow: 0 6px 16px rgba(5, 150, 105, 0.4);
        }
        
        /* Results Section */
        .result-cards {
            display: grid;
            grid-template-columns: 1fr;
            gap: 15px;
        }
        
        .result-card {
            background: var(--gray-100);
            border-radius: 10px;
            padding: 20px;
            border-left: 4px solid var(--primary);
            box-shadow: var(--shadow);
        }
        
        .result-card.profit {
            border-left-color: var(--success);
        }
        
        .result-card.margin {
            border-left-color: var(--warning);
        }
        
        .result-card.markup {
            border-left-color: var(--purple);
        }
        
        .result-title {
            font-size: 0.9rem;
            color: var(--gray-500);
            margin-bottom: 5px;
        }
        
        .result-value {
            font-size: 1.8rem;
            font-weight: 700;
            color: var(--gray-700);
        }
        
        .result-positive {
            color: var(--success);
        }
        
        .result-negative {
            color: var(--danger);
        }
        
        .result-details {
            margin-top: 10px;
            font-size: 0.9rem;
            color: var(--gray-500);
        }
        
        /* Visualization */
        .profit-visualization {
            margin-top: 30px;
            padding: 20px;
            background: var(--gray-100);
            border-radius: 10px;
        }
        
        .visualization-title {
            font-size: 1.1rem;
            font-weight: 600;
            margin-bottom: 15px;
            color: var(--gray-700);
        }
        
        .visualization-bar {
            height: 40px;
            background: var(--gray-300);
            border-radius: 8px;
            overflow: hidden;
            margin-bottom: 15px;
            position: relative;
        }
        
        .bar-cost {
            position: absolute;
            height: 100%;
            background: var(--danger);
            left: 0;
        }
        
        .bar-profit {
            position: absolute;
            height: 100%;
            background: var(--success);
        }
        
        .bar-labels {
            display: flex;
            justify-content: space-between;
            font-size: 0.85rem;
            color: var(--gray-500);
        }
        
        /* Features Section - FIXED */
        .features-section {
            margin-top: 60px;
        }
        
        .features-grid {
            display: grid;
            grid-template-columns: repeat(2, 1fr); /* 2 columns on desktop */
            gap: 30px;
            margin-top: 40px;
        }
        
        .feature-card {
            background: #ffffff;
            padding: 30px;
            border-radius: 12px;
            box-shadow: var(--shadow);
            border: 1px solid var(--gray-300);
            text-align: center;
            transition: all 0.3s ease;
        }
        
        .feature-card:hover {
            transform: translateY(-5px);
            box-shadow: var(--shadow-lg);
        }
        
        .feature-icon {
            font-size: 2.5rem;
            margin-bottom: 20px;
            color: var(--primary);
            display: block; /* Ensure icons display */
        }
        
        .feature-card h4 {
            font-size: 1.2rem;
            font-weight: 600;
            color: var(--gray-700);
            margin-bottom: 15px;
        }
        
        .feature-card p {
            color: var(--gray-500);
            line-height: 1.6;
        }
        
        /* Responsive Design - FIXED FEATURE GRID */
        @media (max-width: 992px) {
            .calculator-main {
                grid-template-columns: 1fr;
            }
        }
        
        @media (max-width: 768px) {
            .profit-calculator-container {
                padding: 15px;
            }
            
            .main-title {
                font-size: 2rem;
            }
            
            .description {
                font-size: 1rem;
            }
            
            .calculator-main {
                padding: 25px;
            }
            
            /* Fixed for mobile: 1 column */
            .features-grid {
                grid-template-columns: 1fr;
                gap: 20px;
            }
            
            .feature-card {
                padding: 25px;
            }
        }
        
        @media (max-width: 480px) {
            .main-title {
                font-size: 1.8rem;
            }
            
            .calculator-main {
                padding: 20px;
            }
            
            .result-value {
                font-size: 1.5rem;
            }
        }
        
        /* Notification */
        .notification {
            position: fixed;
            top: 20px;
            right: 20px;
            padding: 15px 20px;
            border-radius: 8px;
            color: white;
            font-weight: 500;
            z-index: 1000;
            opacity: 0;
            transform: translateX(100%);
            transition: all 0.3s ease;
            max-width: 300px;
        }
        
        .notification-success {
            background: var(--success);
        }
        
        .notification-error {
            background: var(--danger);
        }
        
        .notification-info {
            background: var(--primary);
        }