:root {
      --bg:            #ffffff;
      --bg-soft:       #f9fafb;
      --bg-subtle:     #f3f4f6;
      --border:        #e5e7eb;
      --border-strong: #d1d5db;
      --text:          #111827;
      --text-muted:    #6b7280;
      --text-light:    #9ca3af;

      --blue:          #2563eb;
      --blue-dark:     #1d4ed8;
      --blue-light:    #eff6ff;
      --blue-border:   #bfdbfe;

      --green:         #16a34a;
      --green-light:   #f0fdf4;
      --green-border:  #bbf7d0;

      --amber:         #d97706;
      --amber-light:   #fffbeb;
      --amber-border:  #fde68a;

      --red:           #dc2626;

      --radius-sm:  4px;
      --radius:     8px;
      --radius-lg:  12px;

      --shadow-sm:  0 1px 3px rgba(0,0,0,.07);
      --shadow-md:  0 4px 12px rgba(0,0,0,.08);

      --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    }
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
body {
      font-family: var(--font);
      color: var(--text);
      background: var(--bg);
      line-height: 1.6;
      -webkit-font-smoothing: antialiased;
    }
nav {
      position: sticky; top: 0; z-index: 100;
      background: var(--bg);
      border-bottom: 1px solid var(--border);
      height: 56px;
      display: flex;
      align-items: center;
      gap: 2rem;
      padding: 0 1.5rem;
      overflow-x: auto;
    }
.nav-logo {
      font-weight: 700; font-size: 1.05rem;
      color: var(--text); text-decoration: none; white-space: nowrap;
    }
.nav-links { display: flex; gap: 1.5rem; list-style: none; }
.nav-links a {
      text-decoration: none; color: var(--text-muted);
      font-size: .875rem; font-weight: 500; white-space: nowrap;
      transition: color .15s;
    }
.nav-links a:hover { color: var(--blue); }
.nav-links a.active { color: var(--blue); }
.card {
      background: var(--bg);
      border: 1px solid var(--border);
      border-radius: var(--radius-lg);
      padding: 1.75rem;
      margin-bottom: 1.5rem;
      box-shadow: var(--shadow-sm);
    }
.calc-btn:hover { background: var(--blue-dark); }
.calc-btn:active { transform: scale(.99); }
.section h2 {
      font-size: 1.1875rem; font-weight: 700;
      margin-bottom: .875rem;
      padding-bottom: .5rem;
      border-bottom: 2px solid var(--border);
    }
footer {
      border-top: 1px solid var(--border);
      padding: 1.5rem;
      text-align: center;
      font-size: .8rem; color: var(--text-muted); line-height: 1.6;
    }
.footer-links { display: flex; gap: .875rem; justify-content: center; margin-top: .5rem; flex-wrap: wrap; }
footer a { color: var(--text-muted); text-decoration: none; }
footer a:hover { color: var(--blue); }

.wrap {
      max-width: 760px;
      margin: 0 auto;
      padding: 2.5rem 1.5rem 5rem;
    }
.page-header { margin-bottom: 2rem; }
.badge {
      display: inline-block;
      padding: .25rem .625rem;
      border-radius: 100px;
      font-size: .7rem; font-weight: 700;
      letter-spacing: .05em; text-transform: uppercase;
      background: var(--blue-light);
      color: var(--blue);
      border: 1px solid var(--blue-border);
      margin-bottom: .875rem;
    }
.page-header h1 {
      font-size: 2rem; font-weight: 800; line-height: 1.2;
      margin-bottom: .5rem;
    }
.page-header .subtitle {
      font-size: 1rem; color: var(--text-muted);
    }
.page-header .source-note {
      font-size: .78rem; color: var(--text-light); margin-top: .25rem;
    }
.section-title {
      font-size: .9375rem; font-weight: 700;
      display: flex; align-items: center; gap: .5rem;
      margin-bottom: 1.25rem;
    }
.preset-label {
      font-size: .7rem; font-weight: 700;
      text-transform: uppercase; letter-spacing: .06em;
      color: var(--text-muted);
      margin-bottom: .625rem;
    }
.preset-buttons {
      display: flex; gap: .625rem; flex-wrap: wrap;
      margin-bottom: 1.75rem;
      padding-bottom: 1.5rem;
      border-bottom: 1px solid var(--border);
    }
.preset-btn {
      padding: .5rem 1rem;
      border: 1.5px solid var(--border-strong);
      border-radius: var(--radius);
      background: var(--bg-soft);
      font-size: .875rem; font-weight: 600;
      color: var(--text);
      cursor: pointer;
      transition: all .15s;
      text-align: left;
      line-height: 1.3;
    }
.preset-btn .ps { display: block; font-size: .7rem; font-weight: 400; color: var(--text-muted); margin-top: 1px; }
.preset-btn:hover {
      border-color: var(--blue);
      color: var(--blue);
      background: var(--blue-light);
    }
.preset-btn:hover .ps { color: var(--blue); opacity: .75; }
.preset-btn:active { transform: scale(.97); }
.results-card {
      border: 2px solid var(--blue-border);
      background: var(--blue-light);
    }
.primary-result {
      background: var(--blue);
      border-radius: var(--radius);
      padding: 1.5rem;
      text-align: center;
      margin-bottom: 1.25rem;
      color: white;
    }
.primary-result .pr-label {
      font-size: .7rem; font-weight: 700;
      text-transform: uppercase; letter-spacing: .1em;
      opacity: .8; margin-bottom: .25rem;
    }
.primary-result .pr-value {
      font-size: 2.75rem; font-weight: 800;
      line-height: 1; letter-spacing: -.02em;
    }
.primary-result .pr-unit {
      font-size: .9375rem; font-weight: 500;
      opacity: .85; margin-top: .375rem;
    }
.secondary-results {
      display: grid;
      grid-template-columns: 1fr 1fr 1fr;
      gap: .75rem;
      margin-bottom: 1.25rem;
    }
.r-tile {
      background: var(--bg);
      border: 1px solid var(--border);
      border-radius: var(--radius);
      padding: .875rem;
      text-align: center;
    }
.r-tile .rt-label {
      font-size: .65rem; font-weight: 700;
      text-transform: uppercase; letter-spacing: .05em;
      color: var(--text-muted); margin-bottom: .25rem;
    }
.r-tile .rt-value {
      font-size: 1.3125rem; font-weight: 700;
      line-height: 1.2; color: var(--text);
    }
.r-tile .rt-unit {
      font-size: .65rem; color: var(--text-light); margin-top: .15rem;
    }
.section { margin-bottom: 2.5rem; }
.section p {
      font-size: .9375rem; color: #374151;
      line-height: 1.7; margin-bottom: .75rem;
    }
.ex-box {
      background: var(--bg-subtle);
      border: 1px solid var(--border);
      border-radius: var(--radius);
      padding: 1.25rem 1.5rem;
      margin-top: .875rem;
    }
.ex-box .ex-label {
      font-size: .7rem; font-weight: 700;
      text-transform: uppercase; letter-spacing: .06em;
      color: var(--text-muted); margin-bottom: .75rem;
    }
.ex-steps { list-style: none; padding: 0; }
.ex-steps li {
      display: flex; align-items: baseline; gap: .75rem;
      padding: .5625rem 0;
      border-bottom: 1px solid var(--border);
      font-size: .875rem;
    }
.ex-steps li:last-child { border-bottom: none; }
.ex-steps .sl { font-weight: 600; color: var(--text-muted); min-width: 145px; font-size: .8rem; flex-shrink: 0; }
.ex-steps .sv { font-weight: 700; color: var(--text); }
.tips-list { list-style: none; padding: 0; }
.tips-list li {
      padding: .5rem 0 .5rem 1.375rem;
      position: relative;
      border-bottom: 1px solid var(--border);
      font-size: .875rem; color: #374151; line-height: 1.6;
    }
.tips-list li::before { content: "→"; position: absolute; left: 0; color: var(--blue); font-weight: 700; }
.tips-list li:last-child { border-bottom: none; }
.assum-list { list-style: none; padding: 0; }
.assum-list li {
      display: flex; gap: .625rem; align-items: baseline;
      padding: .5rem 0;
      border-bottom: 1px solid var(--border);
      font-size: .875rem; color: #374151;
    }
.assum-list li:last-child { border-bottom: none; }
.assum-list .ai { color: var(--text-light); flex-shrink: 0; }
.faq-item {
      border: 1px solid var(--border);
      border-radius: var(--radius);
      margin-bottom: .5rem;
      overflow: hidden;
    }
.faq-q {
      width: 100%; background: var(--bg-soft);
      border: none; padding: .875rem 1rem;
      text-align: left; font-size: .875rem; font-weight: 600;
      cursor: pointer; color: var(--text);
      display: flex; justify-content: space-between; align-items: center; gap: 1rem;
      transition: background .15s; font-family: var(--font);
    }
.faq-q:hover { background: var(--bg-subtle); }
.faq-icon { color: var(--text-muted); font-size: 1.125rem; flex-shrink: 0; transition: transform .2s; }
.faq-item.open .faq-icon { transform: rotate(45deg); }
.faq-a {
      display: none;
      padding: .875rem 1rem;
      font-size: .875rem; color: #374151;
      line-height: 1.7;
      border-top: 1px solid var(--border);
    }
.faq-item.open .faq-a { display: block; }
.related-grid { display: grid; grid-template-columns: 1fr 1fr; gap: .625rem; }
.related-link {
      display: block; padding: .75rem 1rem;
      background: var(--bg-soft); border: 1px solid var(--border);
      border-radius: var(--radius); text-decoration: none;
      color: var(--text); font-size: .875rem; font-weight: 500;
      transition: all .15s;
    }
.related-link:hover {
      border-color: var(--blue); color: var(--blue); background: var(--blue-light);
    }