*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
  :root {
    --bg: #FAF9FB; --surface: #FFFFFF; --surface2: #F3F0F9; --text: #1C1917; --muted: #78716C;
    --accent: #7C3AED; --accent-light: #EDE9FE; --accent2: #6D28D9; --border: #E7E5DF;
  }
  body { font-family: 'Plus Jakarta Sans', sans-serif; background: var(--bg); color: var(--text); min-height: 100vh; display: flex; flex-direction: column; }
  header { background: var(--surface); border-bottom: 1px solid var(--border); padding: 0 2rem; height: 60px; display: flex; align-items: center; justify-content: space-between; position: sticky; top: 0; z-index: 100; }
  .logo { font-family: 'Fraunces', serif; font-size: 22px; color: var(--accent2); text-decoration: none; letter-spacing: -0.5px; }
  .logo span { font-style: italic; }
  .nav-links { display: flex; gap: 1.25rem; align-items: center; }
  .nav-links a { font-size: 13px; text-decoration: none; color: var(--muted); font-weight: 500; }
  .nav-links a:hover { color: var(--accent); }
  @media (max-width: 520px) { .nav-links a:not(.nav-home) { display: none; } }
  .ad-banner { background: #f5f5f5; border-bottom: 1px solid var(--border); text-align: center; padding: 10px; }
  .ad-label { font-size: 9px; color: var(--muted); text-transform: uppercase; letter-spacing: 1px; margin-bottom: 3px; }
  .ad-placeholder { height: 90px; display: flex; align-items: center; justify-content: center; color: #ccc; font-size: 12px; border: 1px dashed #ddd; border-radius: 4px; margin: 0 auto; max-width: 728px; }
  .hero { background: linear-gradient(135deg, var(--accent2), var(--accent)); padding: 2.5rem 2rem; text-align: center; color: white; }
  .hero-eyebrow { font-size: 11px; font-weight: 600; text-transform: uppercase; letter-spacing: 0.15em; color: rgba(255,255,255,0.75); margin-bottom: 0.75rem; }
  .hero h1 { font-family: 'Fraunces', serif; font-size: clamp(2rem, 5vw, 3rem); font-weight: 400; line-height: 1.1; margin-bottom: 0.75rem; }
  .hero h1 em { font-style: italic; }
  .hero p { font-size: 15px; color: rgba(255,255,255,0.85); font-weight: 300; max-width: 460px; margin: 0 auto; }
  main { flex: 1; max-width: 720px; margin: 0 auto; width: 100%; padding: 2.5rem 1.5rem; }
  .card { background: var(--surface); border: 1px solid var(--border); border-radius: 24px; padding: 2.5rem; margin-bottom: 1.5rem; box-shadow: 0 1px 3px rgba(0,0,0,0.04); }
  .unit-toggle { display: flex; background: var(--surface2); border-radius: 12px; padding: 4px; margin-bottom: 1rem; }
  .unit-btn { flex: 1; padding: 0.6rem; border: none; border-radius: 9px; font-family: 'Plus Jakarta Sans', sans-serif; font-size: 14px; font-weight: 500; cursor: pointer; transition: all 0.2s; background: transparent; color: var(--muted); }
  .unit-btn.active { background: var(--surface); color: var(--accent2); box-shadow: 0 1px 3px rgba(0,0,0,0.08); }
  .form-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; margin-bottom: 1rem; }
  @media (max-width: 480px) { .form-grid { grid-template-columns: 1fr; } }
  .field { margin-bottom: 1rem; }
  .field label { display: block; font-size: 11px; font-weight: 600; text-transform: uppercase; letter-spacing: 0.08em; color: var(--muted); margin-bottom: 0.5rem; }
  .input-wrap { position: relative; }
  .input-wrap input { width: 100%; padding: 0.85rem 3rem 0.85rem 1rem; border: 1.5px solid var(--border); border-radius: 12px; font-family: 'Plus Jakarta Sans', sans-serif; font-size: 16px; color: var(--text); background: var(--bg); outline: none; transition: border-color 0.2s; }
  .input-wrap input:focus { border-color: var(--accent); background: white; }
  .input-unit { position: absolute; right: 1rem; top: 50%; transform: translateY(-50%); font-size: 13px; color: var(--muted); font-weight: 500; pointer-events: none; }
  .height-row { display: grid; grid-template-columns: 1fr 1fr; gap: 0.5rem; }
  .measure-tip { font-size: 12px; color: var(--muted); line-height: 1.6; margin: -0.25rem 0 1rem; }
  .calc-btn { width: 100%; padding: 1rem; background: var(--accent2); color: white; border: none; border-radius: 14px; font-family: 'Plus Jakarta Sans', sans-serif; font-size: 16px; font-weight: 600; cursor: pointer; transition: background 0.2s, transform 0.1s; letter-spacing: 0.01em; }
  .calc-btn:hover { background: var(--accent); }
  .calc-btn:active { transform: scale(0.99); }
  .result-box { display: none; }
  .result-box.show { display: block; animation: fadeUp 0.4s ease; }
  @keyframes fadeUp { from { opacity: 0; transform: translateY(12px); } to { opacity: 1; transform: translateY(0); } }
  .bf-display { text-align: center; padding: 2rem; border-radius: 20px; margin-bottom: 1rem; border: 2px solid; }
  .bf-number { font-family: 'Fraunces', serif; font-size: clamp(3.5rem, 14vw, 5.5rem); font-weight: 400; line-height: 1; }
  .bf-category { font-size: 18px; font-weight: 600; margin-top: 0.5rem; }
  .bf-desc { font-size: 13px; margin-top: 0.5rem; opacity: 0.85; max-width: 380px; margin-left: auto; margin-right: auto; }
  .bf-display.essential { background: #EFF6FF; border-color: #BFDBFE; color: #1D4ED8; }
  .bf-display.athletes { background: #ECFDF5; border-color: #A7F3D0; color: #065F46; }
  .bf-display.fitness { background: #F0FDF4; border-color: #BBF7D0; color: #15803D; }
  .bf-display.average { background: #FFFBEB; border-color: #FDE68A; color: #92400E; }
  .bf-display.obese { background: #FEF2F2; border-color: #FECACA; color: #991B1B; }
  .stats-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0.75rem; margin-bottom: 1rem; }
  @media (max-width: 400px) { .stats-grid { grid-template-columns: 1fr; } }
  .stat-card { background: var(--surface2); border-radius: 14px; padding: 1rem; text-align: center; }
  .stat-num { font-family: 'Fraunces', serif; font-size: 1.3rem; color: var(--text); font-weight: 400; line-height: 1; }
  .stat-label { font-size: 11px; color: var(--muted); margin-top: 4px; text-transform: uppercase; letter-spacing: 0.06em; }
  .ad-block { background: #f9f9f9; border: 1px dashed #ddd; border-radius: 12px; padding: 1rem; text-align: center; font-size: 11px; color: var(--muted); margin-bottom: 1.5rem; min-height: 260px; display: flex; flex-direction: column; align-items: center; justify-content: center; }
  .info-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 0.75rem; margin-bottom: 1.5rem; }
  @media (max-width: 480px) { .info-grid { grid-template-columns: 1fr; } }
  .info-card { background: var(--surface); border: 1px solid var(--border); border-radius: 16px; padding: 1.25rem; }
  .info-card .icon { font-size: 1.5rem; margin-bottom: 0.5rem; }
  .info-card h2 { font-size: 13px; font-weight: 600; margin-bottom: 0.25rem; }
  .info-card h3 { font-size: 13px; font-weight: 600; margin-bottom: 0.25rem; }
  .info-card p { font-size: 12px; color: var(--muted); line-height: 1.5; }
  .bf-table { width: 100%; border-collapse: collapse; margin-bottom: 1.5rem; font-size: 13px; }
  .bf-table th { text-align: left; padding: 0.6rem 1rem; background: var(--surface2); font-weight: 600; font-size: 11px; text-transform: uppercase; letter-spacing: 0.06em; color: var(--muted); }
  .bf-table td { padding: 0.75rem 1rem; border-bottom: 1px solid var(--border); }
  .bf-table tr:last-child td { border-bottom: none; }
  .dot { display: inline-block; width: 10px; height: 10px; border-radius: 50%; margin-right: 6px; vertical-align: middle; }
  .related-links { background: var(--surface); border: 1px solid var(--border); border-radius: 16px; padding: 1.5rem; margin-bottom: 1.5rem; }
  .related-links h2 { font-size: 12px; font-weight: 600; text-transform: uppercase; letter-spacing: 0.08em; color: var(--muted); margin-bottom: 1rem; }
  .related-links-grid { display: flex; flex-direction: column; gap: 0.6rem; }
  .related-link { display: flex; align-items: center; justify-content: space-between; padding: 0.7rem 1rem; background: var(--surface2); border-radius: 10px; text-decoration: none; color: var(--text); font-size: 13px; font-weight: 500; }
  .related-link span.arrow { color: var(--accent); font-weight: 700; }
  .faq { margin-bottom: 2rem; }
  .faq h2 { font-family: 'Fraunces', serif; font-size: 1.75rem; font-weight: 400; margin-bottom: 1rem; }
  .faq-item { border-bottom: 1px solid var(--border); padding: 1rem 0; }
  .faq-item h3 { font-size: 14px; font-weight: 600; margin-bottom: 0.4rem; }
  .faq-item p { font-size: 13px; color: var(--muted); line-height: 1.6; }
  footer { background: var(--surface); border-top: 1px solid var(--border); padding: 1.5rem 2rem; text-align: center; font-size: 12px; color: var(--muted); }
  footer a { color: var(--accent2); text-decoration: underline; }
  .error-msg { display: none; color: #EF4444; font-size: 13px; margin-top: 0.75rem; text-align: center; }
  .error-msg.show { display: block; }
  .bf-content h2 { font-family: 'Fraunces', serif; font-size: 1.6rem; font-weight: 400; margin: 2rem 0 0.75rem; line-height: 1.2; }
  .bf-content h2 em { font-style: italic; }
  .bf-content p { font-size: 15px; color: #2C2B28; margin-bottom: 1rem; line-height: 1.75; }
  .bf-content strong { font-weight: 600; color: var(--text); }
  .bf-data-table { background: var(--surface); border: 1px solid var(--border); border-radius: 16px; overflow: hidden; margin: 1.5rem 0; }
  .bf-data-table .t-title { font-size: 12px; font-weight: 600; text-transform: uppercase; letter-spacing: 0.08em; color: var(--muted); padding: 1rem 1.25rem 0.75rem; border-bottom: 1px solid var(--border); }
  .bf-data-table table { width: 100%; border-collapse: collapse; font-size: 14px; }
  .bf-data-table th { text-align: left; padding: 0.6rem 1.25rem; background: var(--surface2); font-size: 11px; font-weight: 600; text-transform: uppercase; letter-spacing: 0.06em; color: var(--muted); }
  .bf-data-table td { padding: 0.7rem 1.25rem; border-bottom: 1px solid var(--border); }
  .bf-data-table tr:last-child td { border-bottom: none; }
  .bf-data-table td.hi { font-family: 'Fraunces', serif; font-size: 15px; font-weight: 700; color: var(--accent); }
  @media (max-width: 520px) { .bf-data-table td, .bf-data-table th { padding: 0.5rem 0.75rem; font-size: 12px; } }
  .bf-insight { background: var(--accent-light); border-left: 4px solid var(--accent); border-radius: 0 12px 12px 0; padding: 1.25rem 1.5rem; margin: 1.5rem 0; }
  .bf-insight .i-label { font-size: 10px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.1em; color: var(--accent2); margin-bottom: 0.4rem; }
  .bf-insight p { font-size: 14px; color: var(--text); margin: 0; line-height: 1.6; }
  .bf-formula { background: var(--surface2); padding: 1rem 1.25rem; border-radius: 10px; font-family: monospace; font-size: 13px; color: var(--text); margin: 1rem 0; }
  .bf-mistake-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin: 1.5rem 0; }
  @media (max-width: 520px) { .bf-mistake-grid { grid-template-columns: 1fr; } }
  .bf-mistake-card { background: var(--surface); border: 1px solid var(--border); border-radius: 14px; padding: 1.1rem; }
  .bf-mistake-card h3 { font-size: 13px; font-weight: 600; margin-bottom: 0.25rem; color: var(--text); }
  .bf-mistake-card p { font-size: 12px; color: var(--muted); line-height: 1.5; margin: 0; }