* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.container {
    width: 100%;
    max-width: 500px;
    padding: 20px;
}

h1 {
    color: white;
    text-align: center;
    margin-bottom: 30px;
    font-size: 2.5rem;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.2);
}

.calculator {
    background: white;
    padding: 30px;
    border-radius: 15px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.2);
}

.unit-toggle {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

.unit-toggle button {
    flex: 1;
    padding: 10px;
    border: none;
    background: #f0f0f0;
    cursor: pointer;
    border-radius: 5px;
    font-weight: 600;
    transition: all 0.3s ease;
}

.unit-toggle button.active {
    background: #667eea;
    color: white;
}

.input-group {
    margin-bottom: 20px;
}

.input-field {
    margin-bottom: 15px;
}

.input-field label {
    display: block;
    margin-bottom: 5px;
    color: #333;
    font-weight: 500;
}

.input-field input {
    width: 100%;
    padding: 12px;
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

.input-field input:focus {
    outline: none;
    border-color: #667eea;
}

#calculate-btn {
    width: 100%;
    padding: 15px;
    background: #667eea;
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.3s ease;
}

#calculate-btn:hover {
    background: #764ba2;
}

.result {
    margin-top: 30px;
    text-align: center;
    padding: 20px;
    background: #f8f9fa;
    border-radius: 8px;
}

.result h2 {
    color: #333;
    margin-bottom: 15px;
}

.bmi-value {
    font-size: 2.5rem;
    font-weight: bold;
    color: #667eea;
    margin-bottom: 10px;
}

.bmi-category {
    font-size: 1.2rem;
    color: #666;
    font-weight: 500;
}