@font-face { font-family: 'Inter'; src: url('fonts/inter-v20-latin-regular.woff2') format('woff2'); font-weight: 400; font-style: normal; font-display: optional; }
  @font-face { font-family: 'Inter'; src: url('fonts/inter-v20-latin-600.woff2') format('woff2'); font-weight: 600; font-style: normal; font-display: optional; }
  @font-face { font-family: 'Playfair Display'; src: url('fonts/playfair-display-v40-latin-700.woff2') format('woff2'); font-weight: 700; font-style: normal; font-display: optional; }

  :root {
    --bg: #f3f3f7;
    --bg2: #ebebee;
    --bg3: #e4e4e4;
    --accent: #0066cc;
    --accent2: #1a7add;
    --text: #191a1f;
    --muted: #66656a;
    --border: rgba(1,1,8,0.1);
    --border-accent: rgba(0,102,204,0.3);
    --good: #177245;
    --warn: #9a5b00;
    --mono: 'Inter', sans-serif;
    --sans: 'Playfair Display', serif;
  }

  *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
  html { scroll-behavior: smooth; }
  body { background: var(--bg); color: var(--text); font-family: var(--mono); line-height: 1.7; overflow-x: hidden; font-size: 1rem; -webkit-font-smoothing: antialiased; }
  body::before { content: ''; position: fixed; inset: 0; background-image: linear-gradient(rgba(0,102,204,0.05) 1px, transparent 1px), linear-gradient(90deg, rgba(0,102,204,0.05) 1px, transparent 1px); background-size: 40px 40px; pointer-events: none; z-index: 0; }

  .skip-link { position: fixed; top: 1rem; left: 1rem; z-index: 200; transform: translateY(-160%); padding: 0.65rem 1rem; background: var(--accent); color: #fff; font-size: 0.78rem; font-weight: 600; text-decoration: none; transition: transform 0.2s; }
  .skip-link:focus { transform: translateY(0); }

  nav { position: fixed; top: 0; left: 0; right: 0; z-index: 100; display: flex; align-items: center; justify-content: space-between; padding: 1.2rem 3rem; background: rgba(248,248,250,0.92); backdrop-filter: blur(12px); border-bottom: 1px solid var(--border); }
  .nav-logo { font-family: var(--sans); font-weight: 800; font-size: 1.05rem; letter-spacing: 0.05em; color: var(--text); text-decoration: none; }
  .nav-logo span { color: var(--accent); }
  .nav-links { display: flex; gap: 1.4rem; list-style: none; align-items: center; }
  .nav-links a { color: var(--muted); text-decoration: none; font-size: 0.7rem; letter-spacing: 0.12em; text-transform: uppercase; transition: color 0.2s; white-space: nowrap; }
  .nav-links a:hover, .nav-links a[aria-current="page"] { color: var(--accent); }
  a:focus-visible, button:focus-visible, input:focus-visible, select:focus-visible { outline: 3px solid var(--accent); outline-offset: 4px; border-radius: 8px; }
  .nav-cta { background: var(--accent) !important; color: #fff !important; padding: 0.5rem 1.1rem !important; border-radius: 4px; transition: opacity 0.2s, transform 0.15s !important; text-transform: none !important; letter-spacing: 0.04em !important; }
  .nav-cta:hover { opacity: 0.88 !important; transform: translateY(-1px); }

  main { position: relative; z-index: 1; }
  .page-wrap { max-width: 1100px; margin: 0 auto; padding: 9rem 3rem 6rem; }
  .back-link { display: inline-flex; align-items: center; gap: 0.4rem; font-size: 0.72rem; color: var(--muted); text-decoration: none; letter-spacing: 0.08em; margin-bottom: 2.5rem; transition: color 0.2s; }
  .back-link:hover { color: var(--accent); }
  .post-meta { display: flex; align-items: center; gap: 1rem; margin-bottom: 1.2rem; flex-wrap: wrap; }
  .post-tag { font-size: 0.62rem; padding: 0.18rem 0.55rem; border: 1px solid var(--border); color: var(--muted); letter-spacing: 0.06em; }
  h1 { font-family: var(--sans); font-size: clamp(2rem, 5vw, 3.8rem); font-weight: 800; line-height: 1.05; letter-spacing: -0.02em; color: var(--text); margin-bottom: 1rem; max-width: 13ch; }
  h1 em { font-style: normal; color: var(--accent); }
  h2 { font-family: var(--sans); font-size: clamp(1.45rem, 3vw, 2.1rem); line-height: 1.15; letter-spacing: -0.02em; margin-bottom: 1rem; }
  h3 { font-family: var(--sans); font-size: 1.05rem; line-height: 1.25; margin-bottom: 0.65rem; }
  p { color: var(--muted); font-size: 0.86rem; }

  .hero-grid { display: grid; grid-template-columns: 1.05fr 0.95fr; gap: 4rem; align-items: center; margin-bottom: 4.5rem; }
  .page-intro { font-size: 0.95rem; color: var(--muted); line-height: 1.9; margin-bottom: 2rem; max-width: 58ch; }
  .hero-actions { display: flex; gap: 1rem; flex-wrap: wrap; margin-bottom: 1.4rem; }
  .btn-primary, .btn-outline { display: inline-flex; align-items: center; gap: 0.5rem; padding: 0.75rem 1.5rem; font-family: var(--mono); font-size: 0.8rem; text-decoration: none; letter-spacing: 0.04em; transition: opacity 0.2s, transform 0.15s, background 0.2s; border: 0; cursor: pointer; }
  .btn-primary { background: var(--accent); color: #fff; }
  .btn-primary:hover { opacity: 0.85; transform: translateY(-1px); }
  .btn-outline { border: 1px solid var(--border-accent); color: var(--accent); background: transparent; }
  .btn-outline:hover { background: rgba(0,102,204,0.07); transform: translateY(-1px); }
  .topic-line { font-size: 0.72rem; color: var(--muted); letter-spacing: 0.04em; line-height: 1.9; }
  .signal-panel { background: var(--bg2); border: 1px solid var(--border-accent); padding: 1.5rem; }
  .signal-panel h2 { font-size: 1.25rem; margin-bottom: 1rem; }
  .signal-list { list-style: none; display: grid; gap: 0.7rem; }
  .signal-list li { color: var(--muted); font-size: 0.82rem; padding: 0.7rem 0.8rem; background: var(--bg); border: 1px solid var(--border); }
  .signal-list strong { color: var(--text); }

  section.content-section { margin-top: 4rem; }
  .section-tag { font-size: 0.7rem; letter-spacing: 0.2em; text-transform: uppercase; color: var(--accent); margin-bottom: 1rem; display: flex; align-items: center; gap: 0.8rem; }
  .section-tag::before { content: ''; display: block; width: 24px; height: 1px; background: var(--accent); }
  .section-intro { max-width: 64ch; margin-bottom: 2rem; line-height: 1.9; }

  .calculator-shell { display: grid; grid-template-columns: 1.05fr 0.95fr; gap: 1.2rem; align-items: start; }
  .calculator-form, .results-card, .detail-card, .assumption-card, .formula-card { background: var(--bg2); border: 1px solid var(--border); padding: 1.25rem; }
  .form-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1rem; }
  .field { display: grid; gap: 0.35rem; }
  label { color: var(--text); font-size: 0.76rem; font-weight: 600; letter-spacing: 0.04em; }
  input, select { width: 100%; padding: 0.72rem 0.85rem; background: var(--bg); border: 1px solid var(--border); color: var(--text); font-family: var(--mono); font-size: 0.86rem; }
  input:focus, select:focus { border-color: var(--border-accent); }
  .help-text { color: var(--muted); font-size: 0.7rem; line-height: 1.55; }
  .form-actions { display: flex; gap: 0.8rem; flex-wrap: wrap; margin-top: 1.2rem; }
  .results-card { border-color: var(--border-accent); position: sticky; top: 6.5rem; }
  .total-label { color: var(--muted); font-size: 0.7rem; letter-spacing: 0.16em; text-transform: uppercase; }
  .total-cost { font-family: var(--sans); color: var(--accent); font-size: clamp(2.3rem, 5vw, 4rem); line-height: 1; margin: 0.8rem 0; }
  .total-cost small { color: var(--muted); font-family: var(--mono); font-size: 0.9rem; }
  .result-note { border-top: 1px solid var(--border); padding-top: 1rem; margin-top: 1rem; }
  .breakdown { display: grid; gap: 0.55rem; margin-top: 1.2rem; }
  .breakdown-row { display: flex; justify-content: space-between; gap: 1rem; align-items: baseline; padding: 0.65rem 0; border-bottom: 1px solid var(--border); color: var(--muted); font-size: 0.82rem; }
  .breakdown-row strong { color: var(--text); font-weight: 600; }
  .breakdown-row span:last-child { color: var(--accent); font-weight: 600; white-space: nowrap; }
  .insight-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1rem; margin-top: 1.2rem; }
  .detail-card strong, .assumption-card strong { display: block; color: var(--text); font-size: 0.78rem; margin-bottom: 0.35rem; }
  .detail-card span, .assumption-card span { color: var(--muted); font-size: 0.78rem; line-height: 1.65; }
  .assumptions-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1rem; }
  .formula-card code { display: block; white-space: pre-wrap; color: var(--text); font-size: 0.78rem; line-height: 1.75; background: var(--bg); border: 1px solid var(--border); padding: 1rem; }
  .warning-box { border: 1px solid rgba(180,80,0,0.25); background: rgba(255,190,120,0.14); padding: 1.3rem; max-width: 900px; }
  .warning-box h2 { font-size: 1.2rem; margin-bottom: 0.6rem; }
  .warning-box p { color: #5b4a3f; }
  .cta-panel { margin-top: 4rem; padding: 2rem; background: var(--bg2); border: 1px solid var(--border-accent); display: grid; grid-template-columns: 1fr auto; gap: 2rem; align-items: center; }
  .cta-panel p { margin-top: 0.5rem; }

  .divider { height: 1px; background: var(--border); max-width: 1100px; margin: 0 auto; position: relative; z-index: 1; }
  footer { border-top: 1px solid var(--border); padding: 2rem 3rem; display: flex; justify-content: space-between; align-items: center; max-width: 1100px; margin: 0 auto; font-size: 0.72rem; color: var(--muted); position: relative; z-index: 1; }
  footer a { color: var(--muted); text-decoration: none; }
  footer a:hover { color: var(--accent); }
  ::-webkit-scrollbar { width: 4px; }
  ::-webkit-scrollbar-track { background: var(--bg); }
  ::-webkit-scrollbar-thumb { background: rgba(0,102,204,0.3); border-radius: 2px; }

  @media (max-width: 980px) {
    .hero-grid, .calculator-shell, .cta-panel { grid-template-columns: 1fr; }
    .results-card { position: static; }
    .insight-grid { grid-template-columns: repeat(2, 1fr); }
  }
  @media (max-width: 768px) {
    nav { padding: 1rem 1.5rem; }
    .nav-links { display: none; }
    .page-wrap { padding: 7rem 1.5rem 4rem; }
    .hero-grid { gap: 2rem; }
    h1 { max-width: none; }
    .form-grid, .insight-grid, .assumptions-grid { grid-template-columns: 1fr; }
    footer { padding: 2rem 1.5rem; flex-direction: column; gap: 0.5rem; text-align: center; }
  }
  @media (prefers-reduced-motion: reduce) {
    html { scroll-behavior: auto; }
    *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
  }