:root {
  --bg: #f7f7f7;
  --panel: #ffffff;
  --ink: #1f2328;
  --muted: #666666;
  --line: #dddddd;
  --accent: #2f2f2f;
  --accent-soft: #eeeeee;
}

* {
  box-sizing: border-box;
}

body {
  background: var(--bg);
  color: var(--ink);
  font-family: ui-serif, Georgia, "Times New Roman", serif;
  line-height: 1.6;
  margin: 0;
}

a {
  color: #333333;
}

.site-header {
  background: var(--panel);
  border-bottom: 1px solid var(--line);
  padding: 22px clamp(18px, 4vw, 48px);
}

.brand {
  color: var(--ink);
  display: inline-block;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 1.1rem;
  font-weight: 700;
  text-decoration: none;
}

.site-header p {
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  margin: 4px 0 0;
}

.shell {
  display: grid;
  gap: 36px;
  grid-template-columns: minmax(220px, 280px) minmax(0, 760px);
  margin: 0 auto;
  max-width: 1180px;
  padding: 32px clamp(18px, 4vw, 48px) 64px;
}

.sidebar {
  align-self: start;
  border-right: 1px solid var(--line);
  max-height: calc(100vh - 48px);
  overscroll-behavior: contain;
  overflow-y: auto;
  padding-right: 18px;
  position: sticky;
  scrollbar-gutter: stable;
  top: 24px;
}

.sidebar nav {
  display: grid;
  gap: 18px;
}

.nav-section {
  display: grid;
  gap: 4px;
}

.nav-section + .nav-section {
  border-top: 1px solid var(--line);
  padding-top: 14px;
}

.nav-section h2 {
  color: var(--ink);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 0.72rem;
  letter-spacing: 0;
  line-height: 1.2;
  margin: 0 0 2px;
  text-transform: uppercase;
}

.sidebar a {
  border-radius: 6px;
  color: var(--muted);
  display: block;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 0.88rem;
  line-height: 1.3;
  padding: 7px 9px;
  text-decoration: none;
}

.sidebar a.active,
.sidebar a:hover {
  background: var(--accent-soft);
  color: var(--accent);
}

.content {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: clamp(24px, 5vw, 54px);
}

.content h1 {
  font-size: clamp(2rem, 4vw, 3.2rem);
  line-height: 1.05;
  margin: 0 0 24px;
}

.content h2 {
  border-top: 1px solid var(--line);
  font-size: 1.45rem;
  line-height: 1.2;
  margin: 36px 0 14px;
  padding-top: 28px;
}

.content h3 {
  font-size: 1.05rem;
  margin-top: 26px;
}

.content p,
.content li {
  font-size: 1.06rem;
}

.content blockquote {
  border-left: 4px solid var(--accent);
  color: #4a4a4a;
  margin-left: 0;
  padding-left: 18px;
}

.content .intro {
  background: #f1f1f1;
  border: 1px solid #d8d8d8;
  border-radius: 8px;
  margin-bottom: 28px;
  padding: clamp(20px, 4vw, 34px);
}

.content .intro h1 {
  margin-bottom: 12px;
}

.card {
  border: 1px solid var(--line);
  border-radius: 8px;
  display: block;
  margin: 10px 0;
  padding: 14px 16px;
  text-decoration: none;
}

.card span {
  color: var(--ink);
  display: block;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-weight: 700;
}

.card small {
  color: var(--muted);
  display: block;
  font-family: ui-sans-serif, system-ui, sans-serif;
  margin-top: 4px;
}

.source-ref {
  color: var(--muted);
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-size: 0.92em;
}

@media (max-width: 840px) {
  .shell {
    display: block;
    padding-top: 18px;
  }

  .sidebar {
    border-bottom: 1px solid var(--line);
    border-right: 0;
    margin-bottom: 18px;
    max-height: 38vh;
    overflow: auto;
    padding: 0 0 14px;
    position: static;
  }

  .sidebar nav {
    gap: 16px;
  }
}