:root {
  --blue: #1d5bd0;
  --blue-dk: #1748b0;
  --blue-lt: #eef4ff;
  --navy: #0d1f3c;
  --bg: #edf1f7;
  --card: #fff;
  --border: #dde4ed;
  --text: #111827;
  --muted: #5c6878;
  --xs: #94a3b8;
  --color-warning-bg: #fef3c7; --color-warning-border: #f59e0b;
  --color-info-bg: #dbeafe; --color-info-border: #3b82f6;
  --color-tip-bg: #d1fae5; --color-tip-border: #10b981;
  --color-citation-bg: #f1f5f9; --color-citation-border: #94a3b8;
  --r: 8px;
  --max: 840px;
  --shadow: 0 1px 3px rgba(0,0,0,.07), 0 2px 8px rgba(0,0,0,.05);
  --shadow-sm: 0 1px 2px rgba(0,0,0,.04);
  --font: system-ui, -apple-system, 'Segoe UI', sans-serif;
  --mono: ui-monospace, 'Cascadia Code', 'Fira Code', monospace;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; -webkit-text-size-adjust: 100%; }
body { font-family: var(--font); color: var(--text); background: var(--bg); line-height: 1.65; }
a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; }
h1 { font-size: 1.25rem; font-weight: 800; line-height: 1.2; letter-spacing: -.02em; }
h2 { font-size: .9375rem; font-weight: 700; line-height: 1.3; color: var(--text); }
h3 { font-size: .8125rem; font-weight: 600; }
p { margin-bottom: .75rem; }
p:last-child { margin-bottom: 0; }

/* ── Header ── */
.site-header { background: var(--navy); position: sticky; top: 0; z-index: 100; border-bottom: 1px solid rgba(255,255,255,.06); }
.header-wrap { max-width: var(--max); margin: 0 auto; padding: 0 1rem; display: flex; align-items: center; gap: .875rem; height: 44px; }
.site-logo { font-size: .8125rem; font-weight: 800; color: #fff; letter-spacing: -.01em; flex-shrink: 0; }
.site-logo:hover { opacity: .8; text-decoration: none; }
.header-nav { display: flex; overflow-x: auto; scrollbar-width: none; flex: 1; gap: 0; }
.header-nav::-webkit-scrollbar { display: none; }
.header-nav a { font-size: .7rem; font-weight: 500; color: rgba(255,255,255,.52); padding: .25rem .45rem; border-radius: 4px; white-space: nowrap; transition: color .15s, background .15s; }
.header-nav a:hover { color: #fff; background: rgba(255,255,255,.1); text-decoration: none; }

/* ── Page shell ── */
.page-shell { max-width: var(--max); margin: 0 auto; padding: 0 1rem 3rem; }

/* ── Breadcrumbs ── */
.breadcrumbs { font-size: .71rem; color: var(--muted); padding: .5rem 0 .25rem; }
.breadcrumbs a { color: var(--muted); }
.breadcrumbs a:hover { color: var(--blue); }
.breadcrumbs span { margin: 0 .3rem; }

/* ── Main calc card ── */
.calc-card { background: var(--card); border: 1px solid var(--border); border-radius: var(--r); box-shadow: var(--shadow); overflow: hidden; margin-bottom: .5rem; }
.calc-card-header { padding: 1rem 1.375rem .75rem; }
.calc-title { font-size: 1.1875rem; font-weight: 800; letter-spacing: -.02em; line-height: 1.2; }

/* ── Result display ── */
.result-display { background: linear-gradient(135deg, #0c1e4a 0%, #1a52c2 100%); padding: 1.25rem 1.375rem 1rem; }
.rd-value { font-size: 2.5rem; font-weight: 900; color: #fff; letter-spacing: -.03em; line-height: 1; }
.rd-unit { font-size: 1.1rem; font-weight: 400; color: rgba(255,255,255,.55); margin-left: .25rem; }
.rd-label { font-size: .63rem; font-weight: 600; text-transform: uppercase; letter-spacing: .1em; color: rgba(255,255,255,.38); margin-top: .3rem; }

/* ── Safety alert ── */
.safety-alert { margin: .625rem 1.375rem 0; background: #fef2f2; border: 1px solid #fecaca; border-left: 4px solid #ef4444; padding: .525rem .75rem; border-radius: 0 6px 6px 0; font-size: .8rem; color: #991b1b; }

/* ── Recalc section ── */
.recalc-section { padding: .875rem 1.375rem 1.25rem; border-top: 1px solid var(--border); background: #f7fafd; }
.recalc-label { font-size: .62rem; font-weight: 700; text-transform: uppercase; letter-spacing: .1em; color: var(--xs); margin-bottom: .5rem; }
.recalc-section .calc-form { background: none; border: none; padding: 0; margin: 0; box-shadow: none; }

/* ── Calc form ── */
.calc-form { background: var(--card); border: 1.5px solid var(--border); border-radius: var(--r); padding: 1.125rem; margin: 0; box-shadow: var(--shadow-sm); }
.calc-form label { display: block; font-size: .71rem; font-weight: 600; color: var(--muted); text-transform: uppercase; letter-spacing: .05em; margin-bottom: .2rem; }
.calc-form input, .calc-form select { width: 100%; padding: .5rem .7rem; border: 1.5px solid var(--border); border-radius: 6px; font-size: .9375rem; font-family: var(--font); color: var(--text); background: #fff; margin-bottom: .625rem; transition: border-color .15s, box-shadow .15s; appearance: none; }
.calc-form input:focus, .calc-form select:focus { outline: none; border-color: var(--blue); box-shadow: 0 0 0 3px rgba(29,91,208,.12); }
.calc-form select { background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath fill='%2364748b' d='M6 8L0 0h12z'/%3E%3C/svg%3E"); background-repeat: no-repeat; background-position: right .75rem center; padding-right: 2rem; }
.calc-form button { width: 100%; background: var(--blue); color: #fff; border: none; padding: .6rem 1.5rem; border-radius: 6px; font-size: .9375rem; font-weight: 700; cursor: pointer; transition: background .15s, transform .1s; }
.calc-form button:hover { background: var(--blue-dk); transform: translateY(-1px); }
.calc-form button:active { transform: translateY(0); }

/* ── Detail cards ── */
.detail-card { background: var(--card); border: 1px solid var(--border); border-radius: var(--r); padding: 1.125rem 1.375rem; margin-bottom: .5rem; box-shadow: var(--shadow-sm); }
.detail-card h2 { margin-bottom: .5rem; padding-bottom: .4rem; border-bottom: 1px solid var(--border); }
.method-text { font-size: .875rem; color: var(--muted); line-height: 1.7; }

/* ── Formula block ── */
.formula-block { background: var(--bg); border: 1px solid var(--border); border-radius: 6px; padding: .875rem 1rem; margin: .75rem 0; }
.formula-block .expression { font-family: var(--mono); font-size: .875rem; margin-bottom: .5rem; color: var(--blue); }
.formula-block .variables { font-size: .8rem; display: grid; row-gap: .2rem; }
.formula-block .variables dt { font-family: var(--mono); font-weight: 700; color: var(--blue); }
.formula-block .variables dd { color: var(--muted); padding-left: .5rem; margin-bottom: .15rem; }

/* ── Quick ref ── */
.quick-ref { background: var(--bg); border: 1px solid var(--border); border-radius: 6px; padding: .75rem .875rem; margin: .625rem 0; }
.quick-ref h3 { font-size: .62rem; text-transform: uppercase; letter-spacing: .07em; color: var(--xs); margin: 0 0 .45rem; }
.ref-table { width: 100%; font-size: .8rem; border-collapse: collapse; border: none; margin: 0; }
.ref-table td { padding: .25rem .35rem; border: none; border-bottom: 1px solid var(--border); background: transparent; }
.ref-table tr:last-child td { border-bottom: none; }
.ref-symbol { font-family: var(--mono); font-weight: 700; color: var(--blue); }
.ref-value { text-align: right; font-weight: 500; }

/* ── Related pages ── */
.related-pages { background: var(--card); border: 1px solid var(--border); border-radius: var(--r); padding: .875rem 1.125rem; margin-bottom: .5rem; box-shadow: var(--shadow-sm); }
.related-pages h3 { font-size: .62rem; font-weight: 700; text-transform: uppercase; letter-spacing: .1em; color: var(--xs); margin: 0 0 .5rem; }
.related-grid { display: grid; grid-template-columns: 1fr 1fr; gap: .375rem; }
@media (max-width: 520px) { .related-grid { grid-template-columns: 1fr; } }
.related-card { display: flex; align-items: center; justify-content: space-between; gap: .5rem; padding: .475rem .75rem; border: 1px solid var(--border); border-radius: 6px; background: #f7f9fc; text-decoration: none; transition: border-color .15s, background .15s, transform .1s; }
.related-card:hover { border-color: var(--blue); background: var(--blue-lt); transform: translateY(-1px); text-decoration: none; }
.related-card-content { display: flex; flex-direction: column; gap: .05rem; min-width: 0; }
.related-card-label { font-size: .775rem; font-weight: 600; color: var(--blue); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.related-card-reason { font-size: .675rem; color: var(--muted); line-height: 1.35; }
.related-card-arrow { color: #d1d5db; font-size: .75rem; flex-shrink: 0; }

/* ── Considerations grid ── */
.considerations-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; }
@media (max-width: 560px) { .considerations-grid { grid-template-columns: 1fr; } }

/* ── Content blocks (PRESERVED EXACTLY) ── */
.content-block { border-left: 4px solid; border-radius: 0 8px 8px 0; padding: .75rem 1rem; margin: .75rem 0; }
.content-block.warning { background: var(--color-warning-bg); border-color: var(--color-warning-border); }
.content-block.info { background: var(--color-info-bg); border-color: var(--color-info-border); }
.content-block.tip { background: var(--color-tip-bg); border-color: var(--color-tip-border); }
.content-block.code-citation { background: var(--color-citation-bg); border-color: var(--color-citation-border); }
.content-block .block-title { font-weight: 600; margin-bottom: .25rem; font-size: .9rem; }
.content-block .block-source { font-size: .78rem; color: var(--muted); margin-top: .5rem; }

/* ── Methodology ── */
.methodology-deep-dive { margin: .875rem 0; border: 1px solid var(--border); border-radius: 6px; overflow: hidden; }
.methodology-deep-dive summary { font-weight: 600; font-size: .85rem; cursor: pointer; padding: .575rem .875rem; background: #f7f9fc; list-style: none; }
.methodology-deep-dive summary::-webkit-details-marker { display: none; }
.methodology-deep-dive summary::before { content: '▶  '; font-size: .55rem; }
.methodology-deep-dive[open] summary::before { content: '▼  '; }
.methodology-content { padding: .875rem 1rem; }
.methodology-item { margin-bottom: .7rem; }
.methodology-item p { margin: .15rem 0 0; font-size: .82rem; color: var(--muted); }

/* ── Tables ── */
table { width: 100%; border-collapse: collapse; margin: .875rem 0; font-size: .835rem; border-radius: 6px; overflow: hidden; border: 1px solid var(--border); }
th, td { padding: .475rem .75rem; border-bottom: 1px solid var(--border); text-align: left; }
th { background: #f7f9fc; font-weight: 600; font-size: .74rem; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); }
tr:last-child td { border-bottom: none; }
tr:nth-child(even) td { background: #fafbfd; }

/* ── Ad slots ── */
.ad-slot { background: #f7f9fc; border: 1px dashed var(--border); border-radius: 6px; margin: .5rem 0; }
.ad-slot-header { min-height: 90px; }
.ad-slot-in-content { min-height: 250px; }
.ad-slot-footer { min-height: 90px; }

/* ── Footer ── */
.disclaimer { background: #f7f9fc; border: 1px solid var(--border); border-radius: 6px; padding: .625rem .875rem; font-size: .73rem; color: var(--muted); margin: 1rem 0; }
.site-footer { padding: 1rem 0 .5rem; border-top: 1px solid var(--border); font-size: .73rem; color: var(--muted); }
.site-footer a { color: var(--muted); }
.site-footer a:hover { color: var(--blue); }

/* ── Homepage ── */
.home-hero { background: linear-gradient(135deg, var(--navy) 0%, #1d5bd0 100%); color: #fff; padding: 2rem 1.5rem 1.75rem; margin: .875rem 0 .875rem; border-radius: var(--r); }
.home-hero h1 { color: #fff; font-size: 1.75rem; font-weight: 900; letter-spacing: -.03em; margin-bottom: .4rem; }
.home-hero p { color: rgba(255,255,255,.68); font-size: .875rem; margin: 0; }
.home-section-label { font-size: .63rem; font-weight: 700; text-transform: uppercase; letter-spacing: .09em; color: var(--xs); margin-bottom: .5rem; display: block; }
.calc-card-grid { display: grid; grid-template-columns: 1fr 1fr; gap: .5rem; }
@media (max-width: 480px) { .calc-card-grid { grid-template-columns: 1fr; } }
.calc-tile { background: var(--card); border: 1px solid var(--border); border-radius: var(--r); padding: .875rem 1rem; text-decoration: none; color: var(--text); display: block; box-shadow: var(--shadow-sm); transition: border-color .15s, box-shadow .15s, transform .1s; }
.calc-tile:hover { border-color: var(--blue); box-shadow: var(--shadow); transform: translateY(-1px); text-decoration: none; color: var(--text); }
.calc-tile-title { font-size: .84375rem; font-weight: 700; color: var(--blue); margin-bottom: .25rem; }
.calc-tile-desc { font-size: .76rem; color: var(--muted); line-height: 1.45; }