/* CFA Formula Hub — shared styles */
:root {
  --bg: #f7f8fa;
  --surface: #ffffff;
  --surface-2: #fbfcfd;
  --ink: #0f172a;
  --ink-2: #334155;
  --ink-3: #64748b;
  --ink-4: #94a3b8;
  --line: #e2e8f0;
  --line-2: #cbd5e1;
  --brand: #1a3a5c;
  --brand-2: #2563eb;
  --brand-soft: #eef4fb;
  --accent: #d97706;
  --accent-soft: #fef3c7;
  --green: #059669;
  --green-soft: #d1fae5;
  --red: #dc2626;
  --red-soft: #fee2e2;
  --r: 14px;
  --r-sm: 8px;
  --shadow-sm: 0 1px 2px rgba(15,23,42,.05);
  --shadow: 0 4px 16px rgba(15,23,42,.06);
  --shadow-lg: 0 12px 32px rgba(15,23,42,.10);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b0f17;
    --surface: #131823;
    --surface-2: #1a212e;
    --ink: #f1f5f9;
    --ink-2: #cbd5e1;
    --ink-3: #94a3b8;
    --ink-4: #64748b;
    --line: #283041;
    --line-2: #3a4358;
    --brand: #8fb4d8;
    --brand-2: #60a5fa;
    --brand-soft: #1a2438;
    --accent: #fbbf24;
    --accent-soft: #2a2010;
    --green: #34d399;
    --green-soft: #0f2922;
    --red: #f87171;
    --red-soft: #2a1414;
    --shadow: 0 4px 16px rgba(0,0,0,.4);
  }
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html, body {
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Inter", "Segoe UI", system-ui, sans-serif;
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--brand-2); text-decoration: none; }
a:hover { text-decoration: underline; }

.wrap {
  max-width: 1080px;
  margin: 0 auto;
  padding: 48px 24px 80px;
}

/* === Header / breadcrumb === */
.breadcrumb {
  font-size: 14px;
  color: var(--ink-3);
  margin-bottom: 16px;
}
.breadcrumb a { color: var(--ink-3); }
.breadcrumb a:hover { color: var(--brand-2); }

.page-head {
  margin-bottom: 40px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--line);
}
.page-head .eyebrow {
  font-size: 12px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--brand);
  font-weight: 600;
  margin-bottom: 10px;
}
.page-head h1 {
  font-size: clamp(28px, 4vw, 40px);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.15;
  margin-bottom: 12px;
}
.page-head .subtitle {
  font-size: 17px;
  color: var(--ink-2);
  max-width: 720px;
}
.page-head .meta {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-top: 16px;
  font-size: 13px;
  color: var(--ink-3);
}
.weight-badge {
  display: inline-block;
  padding: 4px 10px;
  background: var(--brand-soft);
  color: var(--brand);
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.02em;
}

/* === Subject grid (landing) === */
.subject-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}
.subject-card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--r);
  padding: 24px;
  transition: all .18s ease;
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow-sm);
}
.subject-card:hover {
  border-color: var(--brand-2);
  transform: translateY(-2px);
  box-shadow: var(--shadow);
  text-decoration: none;
}
.subject-card .num {
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--ink-4);
  font-weight: 600;
}
.subject-card h3 {
  font-size: 18px;
  font-weight: 700;
  margin: 6px 0 4px;
  letter-spacing: -0.01em;
}
.subject-card .vn {
  font-size: 14px;
  color: var(--ink-3);
  margin-bottom: 12px;
}
.subject-card .footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 13px;
  color: var(--ink-3);
}

/* === Module list === */
.module-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.module-item {
  display: flex;
  align-items: center;
  gap: 16px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  padding: 16px 20px;
  text-decoration: none;
  color: inherit;
  transition: all .15s ease;
}
.module-item:hover {
  border-color: var(--brand-2);
  background: var(--surface-2);
  text-decoration: none;
}
.module-item .num {
  flex: 0 0 auto;
  width: 40px;
  height: 40px;
  border-radius: 8px;
  background: var(--brand-soft);
  color: var(--brand);
  display: grid;
  place-items: center;
  font-weight: 700;
  font-size: 14px;
}
.module-item .body { flex: 1; }
.module-item .title {
  font-weight: 600;
  font-size: 15px;
  margin-bottom: 2px;
}
.module-item .vn {
  font-size: 13px;
  color: var(--ink-3);
}
.module-item .arrow {
  color: var(--ink-4);
  font-size: 18px;
}
.module-item.disabled {
  opacity: .5;
  pointer-events: none;
}

/* === Formula card === */
.formula {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--r);
  padding: 24px 28px;
  margin: 24px 0;
  box-shadow: var(--shadow-sm);
}
.formula > h3 {
  font-size: 18px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 14px;
  display: flex;
  align-items: baseline;
  gap: 10px;
}
.formula > h3 .tag {
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--brand);
  background: var(--brand-soft);
  padding: 3px 8px;
  border-radius: 4px;
  font-weight: 600;
}
.formula .equation {
  background: var(--surface-2);
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  padding: 18px 20px;
  margin: 12px 0 16px;
  overflow-x: auto;
  font-size: 1.05em;
}
.formula .desc {
  color: var(--ink-2);
  margin-bottom: 14px;
}
.formula .components {
  margin: 12px 0 0;
}
.formula .components h4 {
  font-size: 13px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-3);
  font-weight: 600;
  margin-bottom: 8px;
}
.formula .components ul {
  list-style: none;
  padding: 0;
}
.formula .components li {
  padding: 6px 0;
  border-bottom: 1px dashed var(--line);
  font-size: 15px;
}
.formula .components li:last-child { border-bottom: none; }
.formula .components li .var {
  display: inline-block;
  min-width: 64px;
  font-weight: 600;
  color: var(--brand);
  font-family: "JetBrains Mono", "SF Mono", Menlo, monospace;
}

/* === Definition block (what / why / when) === */
.definition {
  background: var(--brand-soft);
  border-left: 3px solid var(--brand-2);
  border-radius: var(--r-sm);
  padding: 14px 18px;
  margin: 12px 0 16px;
  font-size: 14.5px;
  line-height: 1.65;
}
.definition .def-row {
  display: block;
  margin: 4px 0;
}
.definition .def-row strong {
  display: inline-block;
  min-width: 88px;
  color: var(--brand);
  font-size: 12px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  font-weight: 700;
}

/* === Visual block (SVG diagrams) === */
.visual {
  background: var(--surface-2);
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  padding: 16px;
  margin: 14px 0;
  text-align: center;
}
.visual svg { max-width: 100%; height: auto; display: block; margin: 0 auto; }
.visual .caption {
  font-size: 12.5px;
  color: var(--ink-3);
  margin-top: 8px;
  font-style: italic;
}
.visual .axis-label { fill: var(--ink-3); font-size: 11px; }
.visual .axis { stroke: var(--line-2); stroke-width: 1; }
.visual .gridline { stroke: var(--line); stroke-width: 0.5; stroke-dasharray: 2 3; }
.visual .curve { fill: none; stroke-width: 2; }
.visual .curve-blue { stroke: var(--brand-2); }
.visual .curve-green { stroke: var(--green); }
.visual .curve-red { stroke: var(--red); }
.visual .curve-amber { stroke: var(--accent); }
.visual .label-text { fill: var(--ink-2); font-size: 11px; font-weight: 600; }
.visual .point { fill: var(--brand-2); }

/* === Sample problem === */
.sample {
  background: var(--accent-soft);
  border: 1px solid #fde68a;
  border-radius: var(--r);
  padding: 20px 24px;
  margin: 16px 0 0;
}
@media (prefers-color-scheme: dark) {
  .sample { border-color: #4a3a14; }
}
.sample .label {
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 700;
  margin-bottom: 8px;
}
.sample .question { color: var(--ink); margin-bottom: 12px; }
.sample details {
  margin-top: 8px;
}
.sample details summary {
  cursor: pointer;
  color: var(--brand-2);
  font-weight: 600;
  font-size: 14px;
  user-select: none;
  padding: 6px 0;
}
.sample details summary:hover { text-decoration: underline; }
.sample details[open] summary { margin-bottom: 8px; }
.sample .solution {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  padding: 14px 18px;
  font-size: 14.5px;
  line-height: 1.7;
}
.sample .solution .step {
  color: var(--ink-2);
  margin: 6px 0;
}
.sample .solution .answer {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px dashed var(--line);
  font-weight: 700;
  color: var(--green);
}

/* === Section heading === */
.section-h {
  font-size: 22px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 40px 0 12px;
  padding-top: 12px;
  border-top: 1px solid var(--line);
}
.section-h:first-of-type { border-top: none; padding-top: 0; }

/* Module nav (prev/next) */
.module-nav {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 56px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}
.module-nav a {
  flex: 1;
  padding: 14px 18px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  text-decoration: none;
  color: var(--ink);
  font-size: 14px;
  transition: all .15s ease;
}
.module-nav a:hover {
  border-color: var(--brand-2);
  background: var(--surface-2);
  text-decoration: none;
}
.module-nav a .label {
  display: block;
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-4);
  margin-bottom: 4px;
}
.module-nav a.next { text-align: right; }
.module-nav a.disabled { opacity: .4; pointer-events: none; }

/* TOC sidebar (optional, on module pages) */
.toc {
  background: var(--surface-2);
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  padding: 16px 20px;
  margin-bottom: 32px;
}
.toc .toc-label {
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-3);
  font-weight: 600;
  margin-bottom: 8px;
}
.toc ol {
  margin: 0;
  padding-left: 20px;
  font-size: 14px;
  columns: 2;
  column-gap: 24px;
}
.toc ol li { padding: 3px 0; }
@media (max-width: 640px) { .toc ol { columns: 1; } }

footer.site-foot {
  margin-top: 80px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
  font-size: 13px;
  color: var(--ink-4);
  text-align: center;
}