:root {
  --paper: #fbfaf7;
  --paper-2: #f3f1ec;
  --ink: #1f1d1a;
  --ink-2: #5a5652;
  --ink-3: #8b8681;
  --line: #dedad3;
  --accent: #b8322b;
  --accent-ink: #ffffff;
  --radius: 10px;
  --font: "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Noto Sans JP", "Yu Gothic", "Meiryo", system-ui, sans-serif;
  --mono: "SFMono-Regular", Menlo, Consolas, "Liberation Mono", monospace;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #15140f;
    --paper-2: #1e1c17;
    --ink: #ebe7df;
    --ink-2: #b7b1a6;
    --ink-3: #8a847a;
    --line: #322f28;
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font);
  line-height: 1.8;
}

/* topbar: index.html と共通の見た目 */
header.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 14px 24px;
  border-bottom: 1px solid var(--line);
  background: var(--paper);
  flex-wrap: wrap;
}
.brand { display: flex; align-items: center; gap: 12px; text-decoration: none; color: inherit; }
.brand-mark {
  display: grid;
  place-items: center;
  flex: none;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--accent);
  color: var(--accent-ink);
  font-family: "Hiragino Mincho ProN", "Yu Mincho", "Noto Serif JP", serif;
  font-size: 22px;
  font-weight: 600;
}
.brand-text h1 { font-size: 18px; margin: 0; }
.brand-text p { margin: 0; font-size: 12px; color: var(--ink-3); }
a.btn {
  display: inline-block;
  padding: 8px 14px;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  color: var(--ink);
  text-decoration: none;
  font-size: 13px;
  white-space: nowrap;
  transition: background-color 0.15s ease;
}
a.btn:hover { background: var(--paper); }
a.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
a.btn.primary:hover { opacity: 0.92; }

/* レイアウト: 目次を左サイドに固定し、本文と並べる */
.layout {
  max-width: 1080px;
  margin: 0 auto;
  padding: 32px 24px 80px;
  display: grid;
  grid-template-columns: 200px minmax(0, 1fr);
  gap: 40px;
  align-items: start;
}
@media (max-width: 860px) {
  .layout { grid-template-columns: 1fr; padding: 24px 18px 64px; }
}

nav.toc {
  position: sticky;
  top: 78px;
  font-size: 13px;
}
@media (max-width: 860px) {
  nav.toc { position: static; margin-bottom: 12px; }
}
nav.toc p.toc-label {
  margin: 0 0 10px;
  font-weight: 600;
  color: var(--ink-3);
  letter-spacing: 0.02em;
  text-transform: uppercase;
  font-size: 11px;
}
nav.toc ol {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 2px;
  border-left: 2px solid var(--line);
}
nav.toc a {
  display: block;
  padding: 6px 0 6px 14px;
  color: var(--ink-2);
  text-decoration: none;
}
nav.toc a:hover { color: var(--accent); }

main { min-width: 0; }

.lead {
  color: var(--ink);
  font-size: 15.5px;
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 20px;
  margin: 0 0 8px;
}

section.chapter {
  padding-top: 12px;
  margin-top: 40px;
  border-top: 1px solid var(--line);
}
section.chapter:first-of-type { margin-top: 32px; }

h2 {
  font-size: 19px;
  margin: 0 0 16px;
  display: flex;
  align-items: baseline;
  gap: 8px;
}
h2 .num {
  color: var(--accent);
  font-variant-numeric: tabular-nums;
}
h3 { font-size: 14.5px; margin: 24px 0 8px; color: var(--ink); }
p { color: var(--ink-2); margin: 0 0 12px; }
ol, ul { color: var(--ink-2); padding-left: 22px; }
li { margin-bottom: 8px; }

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13.5px;
  margin: 12px 0 20px;
  background: var(--paper);
}
th, td {
  border: 1px solid var(--line);
  padding: 8px 10px;
  text-align: left;
  vertical-align: top;
}
th { background: var(--paper-2); font-weight: 600; white-space: nowrap; }

code {
  font-family: var(--mono);
  background: var(--paper-2);
  padding: 1px 6px;
  border-radius: 4px;
  font-size: 0.92em;
}
pre {
  font-family: var(--mono);
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 14px 16px;
  overflow-x: auto;
  font-size: 13px;
  line-height: 1.7;
}

.note {
  border-left: 3px solid var(--accent);
  background: var(--paper-2);
  padding: 10px 14px;
  border-radius: 0 var(--radius) var(--radius) 0;
  font-size: 13.5px;
  margin: 12px 0 20px;
}
.note p:last-child { margin-bottom: 0; }

footer.page-foot {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px 60px;
  color: var(--ink-3);
  font-size: 12.5px;
}