:root {
  --bg: #0b0f17;
  --fg: #e6edf3;
  --muted: #9da7b3;
  --card: #121826;
  --link: #7aa2f7;
  --code: #0f172a;
  --border: #263244;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #ffffff;
    --fg: #111827;
    --muted: #4b5563;
    --card: #f8fafc;
    --link: #2563eb;
    --code: #0b1220;
    --border: #e5e7eb;
  }
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.5;
  background: radial-gradient(circle at top, color-mix(in srgb, var(--accent) 20%, transparent), transparent 55%), var(--bg);
  color: var(--fg);
}

nav {
  position: sticky;
  top: 0;
  background: var(--card);
  border-bottom: 1px solid var(--border);
  padding: 12px 16px;
  z-index: 2;
  display: flex;
  align-items: center;
  gap: 10px;
}

nav a {
  color: var(--fg);
  text-decoration: none;
  font-weight: 600;
}

.nav-home {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: color-mix(in srgb, var(--accent) 15%, transparent);
  font-size: 1.1rem;
}

main {
  max-width: 900px;
  margin: 0 auto;
  padding: 24px 16px 64px 16px;
}

h1, h2, h3 {
  margin-top: 28px;
}

p {
  margin: 10px 0;
  color: var(--fg);
}

ul {
  padding-left: 20px;
}

li {
  margin: 6px 0;
}

a {
  color: var(--link);
}

pre {
  background: var(--code);
  color: var(--fg);
  border: 1px solid var(--border);
  padding: 12px;
  overflow-x: auto;
  border-radius: 8px;
}

code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  font-size: 0.95em;
}

code .tok-keyword { color: rgb(220, 120, 255); }
code .tok-type { color: rgb(100, 200, 255); }
code .tok-string { color: rgb(255, 200, 100); }
code .tok-number { color: rgb(150, 255, 150); }
code .tok-comment { color: rgb(120, 120, 120); }
code .tok-operator { color: rgb(255, 180, 180); }
code .tok-paren { color: rgb(200, 200, 100); }
code .tok-identifier { color: rgb(220, 220, 240); }
code .tok-text { color: var(--fg); }

.spacer {
  height: 10px;
}

.hero {
  max-width: 1000px;
  margin: 32px auto 16px auto;
  padding: 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  background: linear-gradient(135deg, color-mix(in srgb, var(--accent) 25%, transparent), var(--card));
  border: 1px solid var(--border);
  border-radius: 16px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}

.hero-text h1 {
  margin: 0 0 8px 0;
  font-size: 2rem;
}

.hero-text p {
  margin: 0;
  color: var(--muted);
  max-width: 520px;
}

.hero-mascot {
  width: min(280px, 40vw);
  height: auto;
  filter: drop-shadow(0 8px 16px rgba(0, 0, 0, 0.35));
}

.content {
  max-width: 1000px;
  margin: 0 auto;
}

.content.with-sidebar {
  max-width: 1200px;
  display: grid;
  grid-template-columns: minmax(220px, 260px) 1fr;
  gap: 24px;
  align-items: start;
}

.content-body {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.page-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 24px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
}

.sidebar {
  position: sticky;
  top: 72px;
  align-self: start;
  padding: 16px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
}

.sidebar h2 {
  margin-top: 0;
  font-size: 1.1rem;
}

.chapter-nav {
  display: flex;
  gap: 16px;
  margin: 24px 0 0 0;
}

.chapter-link {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 12px 16px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  text-decoration: none;
  color: var(--fg);
  font-weight: 600;
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.18);
  transition: transform 0.15s ease, border-color 0.15s ease;
}

.chapter-link.home {
  flex: 0 0 auto;
  width: 54px;
  min-width: 54px;
  padding: 0;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
}

.chapter-link:hover {
  transform: translateY(-2px);
  border-color: color-mix(in srgb, var(--accent) 60%, var(--border));
}

.chapter-link.next {
  align-items: flex-end;
  text-align: right;
}

.chapter-link .label {
  color: var(--muted);
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.chapter-link .title {
  font-size: 1rem;
}

.chapter-link.disabled {
  opacity: 0.45;
  box-shadow: none;
  cursor: default;
}

.chapter-link.disabled:hover {
  transform: none;
  border-color: var(--border);
}

h2 {
  border-left: 4px solid var(--accent);
  padding-left: 12px;
}

.toc {
  list-style: none;
  padding-left: 0;
}

.toc-group {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 8px 10px;
  margin: 10px 0;
  background: color-mix(in srgb, var(--accent) 8%, transparent);
}

.toc-group summary {
  cursor: pointer;
  font-weight: 700;
  color: var(--fg);
  list-style: none;
  display: flex;
  align-items: center;
  gap: 8px;
}

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

.toc-group summary::before {
  content: "▸";
  color: var(--muted);
  transition: transform 0.15s ease;
}

.toc-group[open] summary::before {
  transform: rotate(90deg);
}

.toc-group .toc {
  margin: 8px 0 0 12px;
  border-left: 2px solid color-mix(in srgb, var(--accent) 35%, var(--border));
  padding-left: 12px;
}

.toc li {
  margin: 10px 0;
}

.toc a {
  font-weight: 600;
}

.toc-item.active a {
  color: var(--fg);
  border-left: 3px solid var(--accent);
  padding-left: 10px;
}

@media (max-width: 960px) {
  .content.with-sidebar {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
  }
}