/* EngEst Pro — Engineering Guides / Newsletter
   Shared stylesheet for static article pages at /articles/*.html
   Light theme, red accent, Inter. */

*, *::before, *::after { box-sizing: border-box; }

:root {
  --bg: #ffffff;
  --surface: #f8fafc;
  --surface-2: #f1f5f9;
  --border: #e2e8f0;
  --text: #1e293b;
  --text-muted: #64748b;
  --text-soft: #94a3b8;
  --heading: #0f172a;
  --accent: #dc2626;
  --accent-dark: #b91c1c;
  --accent-soft: rgba(220, 38, 38, 0.08);
  --navy: #0a1628;
  --radius: 10px;
  --wrap: 760px;
}

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 17px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); }
img { max-width: 100%; height: auto; }

/* ---------- Top nav ---------- */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 12px 24px;
  background: var(--navy);
  color: #fff;
}
.site-nav .brand {
  display: flex;
  align-items: center;
  gap: 9px;
  font-weight: 700;
  font-size: 17px;
  color: #fff;
  text-decoration: none;
}
.site-nav .brand .brand-sub {
  display: block;
  font-size: 10px;
  font-weight: 500;
  color: rgba(255, 255, 255, 0.5);
  letter-spacing: 0.02em;
}
.site-nav .spacer { flex: 1; }
.site-nav a.nav-link {
  color: #fbcaca;
  font-size: 13px;
  font-weight: 600;
  text-decoration: none;
  white-space: nowrap;
}
.site-nav a.nav-cta {
  background: var(--accent);
  color: #fff;
  font-size: 13px;
  font-weight: 700;
  text-decoration: none;
  padding: 8px 16px;
  border-radius: 6px;
  white-space: nowrap;
}

/* ---------- Layout ---------- */
.wrap {
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 32px 24px 72px;
}

.breadcrumb {
  font-size: 13px;
  color: var(--text-soft);
  margin-bottom: 20px;
}
.breadcrumb a { color: var(--text-soft); text-decoration: none; }
.breadcrumb a:hover { color: var(--text-muted); }
.breadcrumb span.sep { margin: 0 7px; }

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 4px 13px;
  font-size: 12px;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 18px;
}

h1 {
  font-size: clamp(1.6rem, 4vw, 2.15rem);
  line-height: 1.25;
  font-weight: 800;
  color: var(--heading);
  letter-spacing: -0.02em;
  margin: 0 0 16px;
}

h2 {
  font-size: 1.28rem;
  line-height: 1.35;
  font-weight: 700;
  color: var(--heading);
  letter-spacing: -0.01em;
  margin: 40px 0 12px;
}

h3 {
  font-size: 1.06rem;
  font-weight: 700;
  color: var(--heading);
  margin: 28px 0 10px;
}

p { margin: 14px 0; }

.lede {
  font-size: 1.12rem;
  color: var(--text-muted);
  line-height: 1.7;
  border-left: 3px solid var(--accent);
  padding-left: 16px;
  margin: 0 0 36px;
}

ul, ol { margin: 14px 0; padding-left: 24px; }
li { margin: 6px 0; }

strong { color: var(--heading); font-weight: 700; }

hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 40px 0;
}

/* ---------- Formula / callout blocks ---------- */
.formula {
  background: var(--surface-2);
  border-left: 3px solid var(--accent);
  border-radius: 0 8px 8px 0;
  padding: 12px 18px;
  margin: 18px 0;
  font-family: "SF Mono", ui-monospace, "Cascadia Code", Consolas, monospace;
  font-size: 0.9rem;
  line-height: 1.7;
  color: var(--heading);
  overflow-x: auto;
}

blockquote {
  margin: 18px 0;
  padding: 4px 0 4px 18px;
  border-left: 3px solid var(--border);
  color: var(--text-muted);
}

/* ---------- Tables ---------- */
.table-wrap {
  overflow-x: auto;
  margin: 18px 0;
  border: 1px solid var(--border);
  border-radius: 8px;
}
table {
  border-collapse: collapse;
  width: 100%;
  font-size: 0.92rem;
}
th, td {
  text-align: left;
  padding: 9px 14px;
  border-bottom: 1px solid var(--border);
}
th {
  background: var(--surface-2);
  font-weight: 700;
  color: var(--heading);
  white-space: nowrap;
}
tr:last-child td { border-bottom: none; }
tbody tr:nth-child(even) { background: var(--surface); }

/* ---------- "Using EngEst Pro" callout ---------- */
.callout {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin: 32px 0;
}
.callout .callout-title {
  font-weight: 700;
  color: var(--heading);
  font-size: 0.95rem;
  margin-bottom: 6px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.callout p { margin: 8px 0 0; font-size: 0.97rem; color: var(--text-muted); }

/* ---------- Ad slot ---------- */
.adslot {
  margin: 32px auto;
  text-align: center;
  min-height: 90px;
  overflow: hidden;
}
.adslot .adslot-label {
  font-size: 10px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-soft);
  margin-bottom: 6px;
}

/* ---------- CTA ---------- */
.cta {
  background: linear-gradient(135deg, #dc2626 0%, #b91c1c 100%);
  border-radius: 14px;
  padding: 30px 28px;
  margin: 44px 0 32px;
  text-align: center;
  color: #fff;
}
.cta h2 {
  color: #fff;
  margin: 0 0 8px;
  font-size: 1.3rem;
}
.cta p {
  color: rgba(255, 255, 255, 0.9);
  font-size: 0.98rem;
  margin: 0 auto 18px;
  max-width: 520px;
}
.cta a.cta-btn {
  display: inline-block;
  background: #fff;
  color: var(--accent-dark);
  font-weight: 700;
  font-size: 0.95rem;
  text-decoration: none;
  padding: 12px 30px;
  border-radius: 8px;
}
.cta .cta-note {
  display: block;
  margin-top: 12px;
  font-size: 0.8rem;
  color: rgba(255, 255, 255, 0.7);
}

/* ---------- Related ---------- */
.related { margin-top: 44px; }
.related h2 { font-size: 1.1rem; margin-bottom: 14px; }
.related-grid { display: grid; gap: 10px; }
.related-grid a {
  display: flex;
  align-items: center;
  gap: 13px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 13px 16px;
  text-decoration: none;
  transition: border-color 0.15s;
}
.related-grid a:hover { border-color: var(--accent); }
.related-grid .r-icon { font-size: 22px; flex-shrink: 0; }
.related-grid .r-title { color: var(--heading); font-size: 0.95rem; font-weight: 600; }
.related-grid .r-meta { color: var(--text-soft); font-size: 0.8rem; }
.related-grid .r-arrow { margin-left: auto; color: var(--text-soft); }

/* ---------- Index page ---------- */
.index-hero { text-align: center; margin-bottom: 44px; }
.index-hero .index-icon { font-size: 34px; }
.index-hero h1 { margin-bottom: 10px; }
.index-hero p { color: var(--text-muted); margin: 6px 0; }
.index-hero .byline { font-size: 0.85rem; color: var(--text-soft); }

.cat-section { margin-bottom: 40px; }
.cat-section h2 {
  font-size: 1.05rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--accent);
  border-bottom: 2px solid var(--border);
  padding-bottom: 8px;
  margin: 0 0 16px;
}
.card {
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 16px 20px;
  margin-bottom: 12px;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.card:hover {
  border-color: var(--accent);
  box-shadow: 0 2px 12px rgba(15, 23, 42, 0.06);
}
.card h3 { margin: 0 0 5px; font-size: 1.02rem; line-height: 1.4; }
.card h3 a { color: var(--heading); text-decoration: none; }
.card h3 a:hover { color: var(--accent); }
.card-num { color: var(--text-soft); font-weight: 600; font-size: 0.85em; margin-right: 2px; }
.card p { margin: 0; color: var(--text-muted); font-size: 0.92rem; line-height: 1.6; }

/* ---------- Footer ---------- */
.site-footer {
  border-top: 1px solid var(--border);
  background: var(--surface);
  padding: 28px 24px;
  text-align: center;
}
.site-footer .foot-links {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 10px 20px;
  margin-bottom: 12px;
  font-size: 0.85rem;
}
.site-footer .foot-links a { color: var(--text-muted); text-decoration: none; }
.site-footer .foot-links a:hover { color: var(--accent); }
.site-footer .foot-meta { color: var(--text-soft); font-size: 0.8rem; margin: 4px 0; }

/* ---------- Responsive ---------- */
@media (max-width: 640px) {
  body { font-size: 16px; }
  .wrap { padding: 24px 18px 56px; }
  .site-nav { padding: 10px 16px; gap: 12px; }
  .site-nav .brand .brand-sub { display: none; }
  h2 { font-size: 1.18rem; }
}