:root {
  --primary: #4338ca;
  --secondary: #312e81;
  --accent: #eab308;
  --bg: #ffffff;
  --surface: #eef2ff;
  --surface-alt: #e0e7ff;
  --text: #312e81;
  --muted: #5d6a80;
  --border: #c7d2fe;
  --row-alt: #eef2ff;
  --radius: 12px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.65;
  font-size: 16px;
}
img, svg { max-width: 100%; height: auto; }
a { color: var(--primary); text-decoration: underline; text-underline-offset: 3px; }
a:hover { color: var(--secondary); }

.container { max-width: 1080px; margin: 0 auto; padding: 0 20px; }

/* Header */
.site-header {
  background: linear-gradient(90deg, var(--secondary), var(--primary));
  color: #eef2ff;
  padding: 14px 0;
  border-bottom: 4px solid var(--accent);
  position: sticky;
  top: 0;
  z-index: 30;
}
.site-header .container { display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap; }
.brand { display: flex; align-items: center; gap: 12px; text-decoration: none; color: #eef2ff; font-weight: 700; }
.brand img { width: 40px; height: 40px; border-radius: 8px; background: #ffffff11; }
.brand-name { font-size: 18px; letter-spacing: 0.5px; }
.brand-tag { font-size: 11px; color: #c7d2fe; letter-spacing: 1px; text-transform: uppercase; }

nav.primary { display: flex; gap: 6px; flex-wrap: wrap; }
nav.primary a {
  color: #eef2ff;
  text-decoration: none;
  padding: 8px 12px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 500;
  transition: background 0.15s;
}
nav.primary a:hover { background: #ffffff22; }
nav.primary a.active { background: var(--accent); color: var(--secondary); font-weight: 700; }

/* Hero */
.hero {
  background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
  color: #eef2ff;
  padding: 56px 0 40px;
  border-bottom: 4px solid var(--accent);
}
.hero-grid { display: grid; grid-template-columns: 1fr; gap: 32px; align-items: center; }
@media (min-width: 780px) { .hero-grid { grid-template-columns: 1.4fr 1fr; } }
.hero h1 {
  font-size: clamp(28px, 4.4vw, 42px);
  margin: 0 0 12px;
  line-height: 1.15;
  letter-spacing: -0.5px;
  color: #ffffff;
}
.hero p.lead { font-size: 18px; margin: 6px 0 8px; color: #e0e7ff; max-width: 60ch; }
.byline { font-size: 14px; color: #c7d2fe; margin: 10px 0 22px; }
.byline strong { color: #eab308; }
.hero-cta { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 16px; }
.btn {
  display: inline-block;
  background: var(--accent);
  color: var(--secondary);
  padding: 12px 22px;
  border-radius: 8px;
  text-decoration: none;
  font-weight: 700;
  border: 2px solid var(--accent);
  transition: transform 0.1s, background 0.15s;
}
.btn:hover { transform: translateY(-1px); background: #facc15; color: var(--secondary); }
.btn.ghost { background: transparent; color: #eef2ff; border-color: #c7d2fe; }
.btn.ghost:hover { background: #ffffff11; color: #ffffff; }

/* Main */
main { padding: 40px 0 60px; }
h2, h3 { color: var(--secondary); line-height: 1.25; }
h2 {
  font-size: clamp(22px, 3vw, 30px);
  margin: 44px 0 14px;
  padding: 12px 18px;
  border-left: 6px solid var(--accent);
  background: var(--surface);
  border-radius: 0 var(--radius) var(--radius) 0;
}
h3 { font-size: 20px; margin: 26px 0 10px; color: var(--primary); }
p { margin: 12px 0; }

/* TOC */
nav.toc {
  background: var(--surface-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin: 28px 0 36px;
}
nav.toc h2 {
  all: unset;
  display: block;
  font-size: 16px;
  font-weight: 700;
  color: var(--secondary);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 10px;
}
nav.toc ol { list-style: none; counter-reset: toc; padding: 0; margin: 0; }
nav.toc ol li {
  counter-increment: toc;
  padding: 4px 0 4px 32px;
  position: relative;
}
nav.toc ol li::before {
  content: counter(toc, decimal-leading-zero);
  position: absolute;
  left: 0;
  top: 4px;
  color: var(--accent);
  font-weight: 700;
  font-family: Georgia, serif;
}
nav.toc a { color: var(--secondary); text-decoration: none; }
nav.toc a:hover { color: var(--primary); text-decoration: underline; }

/* Lists */
main ul { list-style: none; padding-left: 0; }
main ul li {
  position: relative;
  padding-left: 26px;
  margin: 8px 0;
}
main ul li::before {
  content: "▶";
  color: var(--accent);
  position: absolute;
  left: 0;
  top: 1px;
  font-size: 12px;
}

main ol {
  list-style: none;
  counter-reset: ol;
  padding-left: 0;
}
main ol li {
  counter-increment: ol;
  position: relative;
  padding-left: 42px;
  margin: 12px 0;
}
main ol li::before {
  content: counter(ol);
  position: absolute;
  left: 0;
  top: 0;
  width: 28px;
  height: 28px;
  background: var(--primary);
  color: var(--accent);
  border-radius: 50%;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 13px;
}

/* Table */
.table-wrap { overflow-x: auto; margin: 20px 0; border-radius: var(--radius); border: 1px solid var(--border); }
table { width: 100%; border-collapse: collapse; font-size: 15px; }
th, td { padding: 12px 14px; text-align: left; border-bottom: 1px solid var(--border); }
thead th {
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  color: var(--accent);
  font-weight: 700;
  letter-spacing: 0.3px;
}
tbody tr:nth-child(even) { background: var(--row-alt); }
tbody tr:hover { background: var(--surface-alt); }

/* Callout */
.callout {
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 5px solid var(--accent);
  padding: 16px 20px;
  border-radius: var(--radius);
  margin: 22px 0;
}
.callout strong { color: var(--secondary); }

/* Figure */
figure { margin: 24px 0; text-align: center; }
figure img, figure svg { border-radius: var(--radius); }
figcaption { font-size: 13px; color: var(--muted); margin-top: 8px; }

/* FAQ */
details {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0;
  margin: 10px 0;
  transition: background 0.15s;
}
details[open] { background: var(--surface-alt); }
details summary {
  padding: 14px 18px;
  cursor: pointer;
  font-weight: 600;
  color: var(--secondary);
  list-style: none;
  position: relative;
  padding-right: 44px;
}
details summary::-webkit-details-marker { display: none; }
details summary::after {
  content: "▼";
  position: absolute;
  right: 18px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--accent);
  font-size: 12px;
  transition: transform 0.2s;
}
details[open] summary::after { transform: translateY(-50%) rotate(180deg); }
details > *:not(summary) { padding: 0 18px 16px; margin: 0; }

/* Author box */
.author-box {
  display: grid;
  grid-template-columns: 96px 1fr;
  gap: 18px;
  align-items: center;
  padding: 22px;
  border-radius: var(--radius);
  background: linear-gradient(135deg, var(--surface-alt), var(--surface));
  border: 1px solid var(--border);
  margin: 40px 0 10px;
}
.author-box img { width: 96px; height: 96px; border-radius: 50%; background: var(--primary); }
.author-box .name { font-weight: 700; color: var(--secondary); font-size: 17px; }
.author-box .role { color: var(--primary); font-size: 13px; text-transform: uppercase; letter-spacing: 1px; margin-bottom: 6px; }
.author-box p { margin: 0; color: var(--text); font-size: 15px; }

/* Sub-page cards */
.card-grid { display: grid; grid-template-columns: 1fr; gap: 18px; margin: 28px 0; }
@media (min-width: 700px) { .card-grid { grid-template-columns: repeat(3, 1fr); } }
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  transition: transform 0.15s, box-shadow 0.15s;
}
.card:hover { transform: translateY(-2px); box-shadow: 0 8px 24px -12px rgba(67, 56, 202, 0.35); }
.card h3 { margin-top: 0; }
.card a { display: inline-block; margin-top: 8px; color: var(--primary); font-weight: 700; text-decoration: none; }
.card a:hover { text-decoration: underline; }

/* Footer */
footer.site-footer {
  background: var(--secondary);
  color: #c7d2fe;
  padding: 36px 0 24px;
  margin-top: 40px;
  border-top: 4px solid var(--accent);
}
footer .foot-grid { display: grid; grid-template-columns: 1fr; gap: 24px; }
@media (min-width: 700px) { footer .foot-grid { grid-template-columns: 2fr 1fr 1fr; } }
footer h3 { color: #eab308; font-size: 14px; text-transform: uppercase; letter-spacing: 1px; margin: 0 0 10px; }
footer a { color: #eef2ff; text-decoration: none; display: block; padding: 3px 0; font-size: 14px; }
footer a:hover { color: var(--accent); text-decoration: underline; }
footer .disclaimer { border-top: 1px solid #4338ca; margin-top: 24px; padding-top: 16px; font-size: 12px; color: #a5b4fc; }

@media (max-width: 700px) {
  nav.primary { justify-content: center; width: 100%; }
  .hero { padding: 40px 0 30px; }
  h2 { padding: 10px 14px; }
}

@media (max-width: 500px) {
  .author-box { grid-template-columns: 1fr; text-align: center; }
  .author-box img { margin: 0 auto; }
}

/* a11y additions */
.skip-link{position:absolute;left:-9999px;top:0;background:var(--primary);color:#fff;padding:10px 16px;border-radius:4px;z-index:1000;text-decoration:none;font-weight:700}
.skip-link:focus{left:12px;top:12px}
a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid var(--accent);outline-offset:2px}
@media (prefers-reduced-motion: reduce){*,*::before,*::after{transition-duration:.01ms !important;animation-duration:.01ms !important}}