* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            min-height: 100vh;
            padding: 40px 20px;
        }
        .container {
            max-width: 600px;
            margin: 0 auto;
            background: white;
            border-radius: 20px;
            padding: 40px;
            box-shadow: 0 20px 60px rgba(0,0,0,0.3);
        }
        h1 {
            text-align: center;
            color: #333;
            margin-bottom: 30px;
            font-size: 2em;
        }
        .units-toggle {
            display: flex;
            gap: 10px;
            margin-bottom: 30px;
            justify-content: center;
        }
        .unit-btn {
            padding: 10px 30px;
            border: 2px solid #667eea;
            background: white;
            border-radius: 8px;
            cursor: pointer;
            font-weight: 600;
            transition: all 0.3s;
        }
        .unit-btn.active {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
        }
        .input-group {
            margin-bottom: 20px;
        }
        label {
            display: block;
            margin-bottom: 8px;
            color: #555;
            font-weight: 600;
        }
        input {
            width: 100%;
            padding: 12px;
            border: 2px solid #e0e0e0;
            border-radius: 8px;
            font-size: 16px;
            transition: border-color 0.3s;
        }
        input:focus {
            outline: none;
            border-color: #667eea;
        }
        .result {
            background: #f9f9f9;
            padding: 30px;
            border-radius: 12px;
            margin: 30px 0;
            text-align: center;
            display: none;
        }
        .result.show {
            display: block;
        }
        .bmi-value {
            font-size: 3em;
            font-weight: bold;
            margin-bottom: 10px;
        }
        .bmi-category {
            font-size: 1.5em;
            margin-bottom: 15px;
        }
        .bmi-description {
            color: #666;
            line-height: 1.6;
        }
        .bmi-chart {
            background: white;
            padding: 20px;
            border-radius: 8px;
            margin-top: 20px;
        }
        .chart-item {
            display: flex;
            justify-content: space-between;
            padding: 10px;
            margin: 5px 0;
            border-radius: 6px;
        }
        .underweight { background: #3498db; color: white; }
        .normal { background: #2ecc71; color: white; }
        .overweight { background: #f39c12; color: white; }
        .obese { background: #e74c3c; color: white; }
        button {
            width: 100%;
            padding: 14px;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            border: none;
            border-radius: 8px;
            font-size: 16px;
            font-weight: 600;
            cursor: pointer;
            transition: transform 0.2s;
            margin-bottom: 10px;
        }
        button:hover {
            transform: translateY(-2px);
        }
        button.secondary {
            background: linear-gradient(135deg, #95a5a6 0%, #7f8c8d 100%);
        }