:root {
  --primary: #0891b2;
  --primary-dark: #0e7490;
  --primary-light: #ecfeff;
  --green: #16a34a;
  --green-light: #f0fdf4;
  --yellow: #d97706;
  --yellow-light: #fffbeb;
  --orange: #ea580c;
  --red: #dc2626;
  --text: #1f2937;
  --text-light: #6b7280;
  --border: #e5e7eb;
  --white: #fff;
  --shadow: 0 2px 8px rgba(0,0,0,0.08);
  --radius: 12px;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif; background: #f9fafb; color: var(--text); line-height: 1.6; }
.container { max-width: 1100px; margin: 0 auto; padding: 0 16px; }

header { background: linear-gradient(135deg, #164e63 0%, var(--primary) 100%); color: white; padding: 32px 0 28px; text-align: center; }
header h1 { font-size: clamp(1.5rem, 4vw, 2.2rem); font-weight: 700; margin-bottom: 8px; }
.subtitle { font-size: 0.92rem; opacity: 0.9; }

.calculator-layout { display: grid; grid-template-columns: 1fr 1.1fr; gap: 24px; margin: 32px 0 24px; }
@media (max-width: 768px) { .calculator-layout { grid-template-columns: 1fr; } }

.input-panel, .result-panel { background: var(--white); border-radius: var(--radius); padding: 24px; box-shadow: var(--shadow); }
.panel-title { font-size: 1.05rem; font-weight: 700; color: var(--primary); margin-bottom: 18px; padding-bottom: 10px; border-bottom: 2px solid var(--primary-light); }

.unit-toggle { display: flex; background: #f3f4f6; border-radius: 8px; padding: 3px; margin-bottom: 20px; gap: 3px; }
.unit-btn { flex: 1; border: none; background: none; padding: 8px; border-radius: 6px; font-size: 0.85rem; font-weight: 600; cursor: pointer; color: var(--text-light); transition: all 0.2s; }
.unit-btn.active { background: white; color: var(--primary); box-shadow: 0 1px 4px rgba(0,0,0,0.1); }

.form-group { margin-bottom: 18px; }
.form-group > label { display: block; font-weight: 600; font-size: 0.9rem; margin-bottom: 6px; }
.optional { font-weight: 400; font-size: 0.8rem; color: var(--text-light); }
.input-suffix { display: flex; align-items: center; border: 1.5px solid var(--border); border-radius: 8px; overflow: hidden; }
.input-suffix:focus-within { border-color: var(--primary); }
.suffix { padding: 9px 10px; background: #f3f4f6; font-size: 0.85rem; color: var(--text-light); white-space: nowrap; }
.input-suffix input { flex: 1; border: none; outline: none; padding: 9px 12px; font-size: 0.95rem; }
.height-imperial-row { display: flex; gap: 8px; }
.height-imperial-row .input-suffix { flex: 1; }
select { width: 100%; border: 1.5px solid var(--border); border-radius: 8px; padding: 9px 10px; font-size: 0.9rem; outline: none; background: white; }
select:focus { border-color: var(--primary); }

.empty-state { text-align: center; color: var(--text-light); padding: 40px 20px; font-size: 0.9rem; }

/* BMI gauge */
.bmi-gauge-wrap { margin-bottom: 20px; }
.bmi-number { text-align: center; margin-bottom: 12px; }
.bmi-value { font-size: 3.5rem; font-weight: 700; line-height: 1; }
.bmi-category-badge { display: inline-block; padding: 4px 14px; border-radius: 20px; font-size: 0.9rem; font-weight: 700; margin-top: 6px; }
.bmi-underweight { color: #1d4ed8; background: #dbeafe; }
.bmi-normal { color: var(--green); background: var(--green-light); }
.bmi-overweight { color: var(--yellow); background: var(--yellow-light); }
.bmi-obese1 { color: var(--orange); background: #fff7ed; }
.bmi-obese2, .bmi-obese3 { color: var(--red); background: #fef2f2; }

/* Gauge bar */
.gauge-bar { height: 14px; border-radius: 7px; background: linear-gradient(to right, #93c5fd 0%, #86efac 25%, #fde047 55%, #fb923c 75%, #f87171 100%); position: relative; margin-bottom: 6px; }
.gauge-marker { position: absolute; top: -4px; width: 4px; height: 22px; background: #1f2937; border-radius: 2px; transform: translateX(-50%); transition: left 0.4s; }
.gauge-labels { display: flex; justify-content: space-between; font-size: 0.72rem; color: var(--text-light); }

/* Result cards */
.result-cards { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-bottom: 16px; }
.result-card { background: var(--primary-light); border-radius: 10px; padding: 12px; text-align: center; }
.rc-label { font-size: 0.75rem; color: var(--text-light); font-weight: 600; margin-bottom: 4px; }
.rc-value { font-size: 1.05rem; font-weight: 700; color: var(--primary); }

.healthy-range-box { background: var(--green-light); border: 1px solid #86efac; border-radius: 10px; padding: 14px; margin-bottom: 14px; }
.healthy-range-box h3 { font-size: 0.9rem; color: var(--green); margin-bottom: 8px; }
.range-row { display: flex; justify-content: space-between; font-size: 0.88rem; margin-bottom: 4px; }
.range-val { font-weight: 700; color: var(--green); }

.tip-box { background: #fef9c3; border: 1px solid #fde047; border-radius: 8px; padding: 12px; font-size: 0.83rem; }

/* Tables */
.table-section, .chart-section { background: var(--white); border-radius: var(--radius); padding: 24px; box-shadow: var(--shadow); margin-bottom: 24px; }
.table-section h2, .chart-section h2 { font-size: 1.05rem; margin-bottom: 14px; }
.table-wrapper { overflow-x: auto; }
.bmi-table { width: 100%; border-collapse: collapse; font-size: 0.85rem; }
.bmi-table th { background: var(--primary); color: white; padding: 8px 12px; text-align: center; }
.bmi-table td { padding: 8px 12px; border-bottom: 1px solid var(--border); text-align: center; }
.cat-underweight td { color: #1d4ed8; }
.cat-normal td { color: var(--green); font-weight: 600; }
.cat-overweight td { color: var(--yellow); }
.cat-obese1 td { color: var(--orange); }
.cat-obese2 td, .cat-obese3 td { color: var(--red); }
.table-note { font-size: 0.78rem; color: var(--text-light); margin-top: 8px; }

/* FAQ */
.faq-section { background: var(--white); border-radius: var(--radius); padding: 24px; box-shadow: var(--shadow); margin-bottom: 32px; }
.faq-section h2 { font-size: 1.05rem; margin-bottom: 14px; }
.faq-item { border-bottom: 1px solid var(--border); }
.faq-item:last-child { border-bottom: none; }
.faq-question { width: 100%; background: none; border: none; text-align: left; padding: 14px 0; font-size: 0.92rem; font-weight: 600; cursor: pointer; display: flex; justify-content: space-between; align-items: center; color: var(--text); gap: 12px; }
.faq-icon { color: var(--primary); font-size: 1.1rem; min-width: 20px; text-align: center; transition: transform 0.2s; }
.faq-question.open .faq-icon { transform: rotate(45deg); }
.faq-answer { display: none; padding: 0 0 14px; font-size: 0.88rem; line-height: 1.7; }
.faq-answer p { margin-bottom: 8px; }

footer { background: #1f2937; color: #9ca3af; padding: 24px 0; text-align: center; }
footer a { color: #9ca3af; text-decoration: underline; margin: 0 6px; }
.disclaimer { font-size: 0.78rem; margin-top: 8px; }