:root {
    --primary-color: #4a90e2;
    --primary-hover: #357abd;
    --bg-color: #f0f2f5;
    --card-bg: #ffffff;
    --text-color: #333;
    --text-light: #666;
    --border-color: #ddd;
    --success-color: #2ecc71;
    --warning-color: #f1c40f;
    --danger-color: #e74c3c;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 20px;
}

.container {
    max-width: 500px;
    width: 100%;
    text-align: center;
}

h1 {
    margin-bottom: 10px;
    color: var(--primary-color);
}

.subtitle {
    margin-bottom: 30px;
    color: var(--text-light);
}

.calculator-card {
    background: var(--card-bg);
    padding: 30px;
    border-radius: 15px;
    box-shadow: var(--shadow);
    margin-bottom: 30px;
}

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

.input-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: var(--text-light);
}

.input-group input {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 16px;
    box-sizing: border-box;
    transition: border-color 0.3s;
}

.input-group input:focus {
    outline: none;
    border-color: var(--primary-color);
}

button {
    width: 100%;
    padding: 15px;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 18px;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.3s;
}

button:hover {
    background-color: var(--primary-hover);
}

#result-container {
    margin-top: 30px;
    padding-top: 20px;
    border-top: 2px solid var(--bg-color);
    animation: fadeIn 0.5s ease-in;
}

.hidden {
    display: none;
}

.bmi-value {
    font-size: 48px;
    font-weight: bold;
    color: var(--primary-color);
}

.bmi-category {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 10px;
}

#bmi-message {
    color: var(--text-light);
    font-style: italic;
}

.info-section {
    background: var(--card-bg);
    padding: 20px;
    border-radius: 15px;
    box-shadow: var(--shadow);
}

.info-section h2 {
    font-size: 20px;
    margin-bottom: 15px;
}

table {
    width: 100%;
    border-collapse: collapse;
}

th, td {
    padding: 12px;
    border-bottom: 1px solid var(--border-color);
    text-align: left;
}

th {
    background-color: #fafafa;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 400px) {
    .container {
        padding: 10px;
    }
}