:root {
  --bg: #fafaf7;
  --panel: #ffffff;
  --ink: #1a1a1a;
  --muted: #6b6b6b;
  --line: #e7e4dc;
  --accent: #8b3a2f;
  --accent-soft: #f2e8e4;
  --code: #f4f1ea;
}
* { box-sizing: border-box; }
html, body { margin: 0; height: 100%; }
body {
  font-family: -apple-system, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  background: var(--bg);
  color: var(--ink);
  display: grid;
  grid-template-columns: 320px 1fr;
  height: 100vh;
}
#sidebar {
  background: var(--panel);
  border-right: 1px solid var(--line);
  display: flex;
  flex-direction: column;
  min-height: 0;
}
#sidebar header {
  padding: 18px 18px 12px;
  border-bottom: 1px solid var(--line);
}
#sidebar h1 {
  margin: 0 0 12px;
  font-size: 18px;
  letter-spacing: 0.5px;
  color: var(--accent);
}
#search {
  width: 100%;
  padding: 8px 10px;
  border: 1px solid var(--line);
  border-radius: 6px;
  font-size: 13px;
  background: var(--bg);
}
#search:focus { outline: none; border-color: var(--accent); }
#tabs {
  display: flex;
  padding: 8px;
  gap: 4px;
  border-bottom: 1px solid var(--line);
}
#tabs button {
  flex: 1;
  padding: 6px 8px;
  background: transparent;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  font-size: 13px;
  color: var(--muted);
}
#tabs button.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
#tree { flex: 1; overflow-y: auto; padding: 8px 0; }
.book { margin-bottom: 2px; }
.book-name {
  padding: 6px 18px;
  font-size: 14px;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  user-select: none;
}
.book-name:hover { background: var(--accent-soft); }
.book-name .caret { color: var(--muted); font-size: 10px; transition: transform 0.15s; }
.book.open .caret { transform: rotate(90deg); }
.chapters { display: none; padding: 4px 0 8px; }
.book.open .chapters { display: block; }
.chap {
  padding: 4px 18px 4px 36px;
  font-size: 13px;
  color: var(--muted);
  cursor: pointer;
}
.chap:hover { color: var(--ink); background: var(--accent-soft); }
.chap.active { color: var(--accent); font-weight: 600; background: var(--accent-soft); }

#content {
  overflow-y: auto;
  padding: 28px 48px 80px;
}
#meta {
  font-size: 13px;
  color: var(--muted);
  margin-bottom: 6px;
}
#versions {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-bottom: 20px;
}
#versions button {
  padding: 4px 10px;
  border: 1px solid var(--line);
  background: var(--panel);
  border-radius: 14px;
  cursor: pointer;
  font-size: 12px;
  color: var(--muted);
}
#versions button.active { background: var(--accent); color: white; border-color: var(--accent); }
#article {
  max-width: 780px;
  line-height: 1.85;
  font-size: 15.5px;
}
.placeholder { color: var(--muted); padding: 60px 0; }
.placeholder h2 { color: var(--ink); margin-top: 0; }
#article h1, #article h2, #article h3 { color: var(--accent); margin-top: 1.6em; }
#article h1 { font-size: 22px; }
#article h2 { font-size: 18px; }
#article h3 { font-size: 16px; }
#article blockquote {
  border-left: 3px solid var(--accent);
  padding: 4px 16px;
  color: var(--muted);
  margin: 16px 0;
  background: var(--accent-soft);
}
#article code {
  background: var(--code);
  padding: 1px 5px;
  border-radius: 3px;
  font-size: 0.9em;
}
#article pre { background: var(--code); padding: 14px; border-radius: 6px; overflow-x: auto; }
#article a { color: var(--accent); }
#article hr { border: none; border-top: 1px solid var(--line); margin: 28px 0; }

@media (max-width: 720px) {
  body { grid-template-columns: 1fr; grid-template-rows: auto 1fr; }
  #sidebar { max-height: 45vh; }
  #content { padding: 20px; }
}