:root {
    --primary-color: #2563eb;
    --secondary-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --success-color: #22c55e;
    --background: #ffffff;
    --surface: #f8fafc;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border: #e2e8f0;
}

[data-theme="dark"] {
    --background: #0f172a;
    --surface: #1e293b;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --border: #334155;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 20px;
}

header {
    text-align: center;
    margin-bottom: 2rem;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

header p {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

.input-section {
    background: var(--surface);
    border-radius: 16px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.input-section h2,
.input-section h3 {
    margin-bottom: 1.5rem;
    color: var(--primary-color);
}

.input-section h3 {
    font-size: 1.2rem;
    margin-top: 2rem;
    margin-bottom: 1rem;
}

.optional-hint {
    margin-bottom: 1rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
    font-style: italic;
}

.optional-hint.complete {
    color: var(--success-color);
    font-style: normal;
    font-weight: 600;
}

.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-bottom: 1rem;
}

.form-group {
    display: flex;
    flex-direction: column;
}

.form-group label {
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
}

.form-group input,
.form-group select {
    padding: 0.75rem;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    background: var(--background);
    color: var(--text-primary);
    transition: border-color 0.2s;
}

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

#calculate {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 1rem 2rem;
    border: none;
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s;
    width: 100%;
    margin-top: 1rem;
}

#calculate:hover {
    transform: translateY(-1px);
}

.results-section {
    margin-bottom: 2rem;
}

.results-section h2 {
    text-align: center;
    margin-bottom: 2rem;
    color: var(--primary-color);
}

.glance-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.glance-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 1rem;
    text-align: center;
    box-shadow: 0 10px 20px rgba(0,0,0,0.05);
}

.glance-card p {
    margin: 0;
    color: var(--text-secondary);
    font-size: 0.85rem;
    letter-spacing: 0.03em;
    text-transform: uppercase;
}

.glance-card strong {
    display: block;
    font-size: 1.8rem;
    margin: 0.2rem 0;
}

.glance-card span {
    color: var(--text-secondary);
    font-size: 0.85rem;
}

.metric-card {
    background: var(--surface);
    border-radius: 16px;
    padding: 1.5rem;
    margin-bottom: 1rem;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    transition: transform 0.2s;
}

.metric-card:hover {
    transform: translateY(-2px);
}

.metric-card h3 {
    color: var(--primary-color);
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
}

.metric-value {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.metric-progress {
    height: 6px;
    border-radius: 999px;
    background: rgba(148, 163, 184, 0.3);
    margin-bottom: 0.75rem;
    overflow: hidden;
}

.metric-progress-bar {
    height: 100%;
    width: 0;
    border-radius: inherit;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    transition: width 0.3s ease;
}

.metric-category {
    font-weight: 600;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    display: inline-block;
    margin-bottom: 0.75rem;
    font-size: 0.9rem;
}

.metric-category.underweight {
    background: #dbeafe;
    color: #2563eb;
}

.metric-category.normal,
.metric-category.good,
.metric-category.excellent {
    background: #d1fae5;
    color: #059669;
}

.metric-category.overweight,
.metric-category.warning {
    background: #fef3c7;
    color: #d97706;
}

.metric-category.obese,
.metric-category.high {
    background: #fee2e2;
    color: #dc2626;
}

.metric-explanation {
    color: var(--text-secondary);
    font-size: 0.9rem;
    font-style: italic;
}

.info-section {
    background: var(--surface);
    border-radius: 16px;
    padding: 2rem;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.info-section h2 {
    text-align: center;
    margin-bottom: 2rem;
    color: var(--primary-color);
}

.info-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
}

.info-card {
    background: var(--background);
    padding: 1.5rem;
    border-radius: 12px;
    border: 2px solid var(--border);
}

.info-card h3 {
    color: var(--primary-color);
    margin-bottom: 0.75rem;
    font-size: 1.1rem;
}

.info-card p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

footer {
    text-align: center;
    padding: 2rem 0;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

@media (max-width: 768px) {
    .container {
        padding: 15px;
    }
    
    header h1 {
        font-size: 2rem;
    }
    
    .form-row {
        grid-template-columns: 1fr;
    }
    
    .input-section {
        padding: 1.5rem;
    }
    
    .info-grid {
        grid-template-columns: 1fr;
    }
    
    .metric-value {
        font-size: 1.5rem;
    }
}