:root {
  --bg: #faf9f7;
  --panel: #ffffff;
  --ink: #1f1d1a;
  --muted: #6b665e;
  --line: #e5e1da;
  --accent: #c15f3c;
  --accent-soft: #fdf1ec;
  --code-bg: #f4f2ee;
  --sidebar-w: 288px;
  --topbar-h: 56px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
        "Helvetica Neue", Arial, sans-serif;
  -webkit-text-size-adjust: 100%;
}

/* ---------- top bar ---------- */

.topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  height: var(--topbar-h);
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 0 16px;
  background: var(--panel);
  border-bottom: 1px solid var(--line);
}

#menu-toggle {
  display: none;
  background: none;
  border: 1px solid var(--line);
  border-radius: 6px;
  font-size: 18px;
  line-height: 1;
  padding: 6px 10px;
  cursor: pointer;
  color: var(--ink);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--ink);
  min-width: 0;
}

.brand-badge {
  flex: none;
  background: var(--accent);
  color: #fff;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.06em;
  padding: 4px 9px;
  border-radius: 5px;
}

.brand-text {
  font-size: 14px;
  font-weight: 600;
  color: var(--muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* ---------- layout ---------- */

.layout {
  display: flex;
  align-items: flex-start;
}

#sidebar {
  position: sticky;
  top: var(--topbar-h);
  flex: none;
  width: var(--sidebar-w);
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto;
  padding: 20px 12px 48px;
  background: var(--panel);
  border-right: 1px solid var(--line);
}

.nav-group { margin-bottom: 18px; }

.nav-group h3 {
  margin: 0 0 6px 10px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--muted);
}

.nav-group ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-group a {
  display: block;
  padding: 6px 10px;
  border-radius: 6px;
  font-size: 14px;
  color: var(--ink);
  text-decoration: none;
}

.nav-group a:hover { background: var(--code-bg); }

.nav-group a.active {
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 600;
}

main {
  flex: 1 1 auto;
  min-width: 0;
  padding: 32px 40px 80px;
}

.prose {
  max-width: 820px;
  margin: 0 auto;
}

/* ---------- prose ---------- */

.prose h1 {
  font-size: 30px;
  line-height: 1.25;
  margin: 0 0 20px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--line);
}

.prose h2 {
  font-size: 22px;
  margin: 40px 0 12px;
  padding-top: 8px;
}

.prose h3 { font-size: 17px; margin: 28px 0 8px; }
.prose h4 { font-size: 15px; margin: 20px 0 6px; color: var(--muted); }

.prose p, .prose li { overflow-wrap: break-word; }

.prose a { color: var(--accent); }

.prose hr {
  border: 0;
  border-top: 1px solid var(--line);
  margin: 32px 0;
}

.prose blockquote {
  margin: 20px 0;
  padding: 12px 18px;
  background: var(--panel);
  border-left: 3px solid var(--accent);
  border-radius: 0 6px 6px 0;
  color: var(--muted);
}

.prose blockquote p { margin: 6px 0; }

.prose code {
  background: var(--code-bg);
  padding: 2px 5px;
  border-radius: 4px;
  font-size: 0.88em;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.prose pre {
  background: var(--code-bg);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 14px 16px;
  overflow-x: auto;
  line-height: 1.5;
}

.prose pre code {
  background: none;
  padding: 0;
  font-size: 13px;
}

/* tables */

.prose table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 14px;
  display: block;
  overflow-x: auto;
}

.prose th, .prose td {
  border: 1px solid var(--line);
  padding: 8px 11px;
  text-align: left;
  vertical-align: top;
}

.prose th {
  background: var(--code-bg);
  font-weight: 600;
  white-space: nowrap;
}

.prose tbody tr:nth-child(even) { background: #fcfbf9; }

/* collapsible answers in the question banks */

.prose details {
  margin: 14px 0 22px;
  padding: 0 16px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
}

.prose details[open] { padding-bottom: 6px; }

.prose summary {
  cursor: pointer;
  padding: 11px 0;
  margin: 0 -16px;
  padding-left: 16px;
  padding-right: 16px;
  font-weight: 600;
  font-size: 14px;
  color: var(--accent);
  list-style: none;
}

.prose summary::-webkit-details-marker { display: none; }

.prose summary::before {
  content: "▸ ";
  display: inline-block;
  width: 1em;
}

.prose details[open] > summary::before { content: "▾ "; }

.prose details[open] > summary {
  border-bottom: 1px solid var(--line);
  margin-bottom: 10px;
}

/* task list checkboxes in the readiness checklist */

.prose input[type="checkbox"] { margin-right: 6px; }

/* ---------- pager ---------- */

.pager-row {
  max-width: 820px;
  margin: 48px auto 0;
  padding-top: 20px;
  border-top: 1px solid var(--line);
  display: flex;
  justify-content: space-between;
  gap: 16px;
  font-size: 14px;
}

.pager {
  color: var(--accent);
  text-decoration: none;
  max-width: 46%;
}

.pager:hover { text-decoration: underline; }

/* ---------- mobile ---------- */

@media (max-width: 900px) {
  #menu-toggle { display: block; }

  #sidebar {
    position: fixed;
    top: var(--topbar-h);
    left: 0;
    z-index: 25;
    transform: translateX(-100%);
    transition: transform 0.18s ease;
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
  }

  body.nav-open #sidebar { transform: translateX(0); }

  main { padding: 24px 18px 64px; }

  .prose h1 { font-size: 25px; }
  .brand-text { display: none; }
}