:root {
  --bg: #fdfcf9; --ink: #23211d; --muted: #6f6a5e; --line: #e8e2d5;
  --accent: #1d5c4d; --accent-soft: #e7f0ec; --card: #ffffff;
  --amber-bg: #fdf3e3; --amber-ink: #8a5a00;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 76px; overflow-x: clip; }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Georgia, serif;
  font-size: 17px; line-height: 1.65; overflow-x: clip;
}
.wrap { max-width: 680px; margin: 0 auto; padding: 0 20px 80px; }
.site-header {
  border-bottom: 1px solid var(--line); background: var(--card);
  position: sticky; top: 0; z-index: 10;
}
.site-header .wrap { padding-top: 14px; padding-bottom: 14px; display: flex;
  align-items: center; gap: 12px; }
.brand { font-weight: 700; font-size: 18px; color: var(--ink); text-decoration: none; }
.brand small { font-weight: 400; color: var(--muted); }
.site-nav { margin-left: auto; display: flex; gap: 18px; font-size: 15px; }
.site-nav a { text-decoration: none; color: var(--muted); }
.site-nav a:hover { color: var(--accent); }
.chapter-nav { display: flex; flex-wrap: wrap; gap: 8px; margin: 18px 0 6px; }
.chapter-nav a {
  font-size: 14px; text-decoration: none; color: var(--muted); background: var(--card);
  border: 1px solid var(--line); border-radius: 999px; padding: 4px 13px;
}
.chapter-nav a:hover { border-color: var(--accent); color: var(--accent); }
.chapter-jump { display: none; }
.discuss-link {
  font-size: 14px; font-weight: 600; text-decoration: none; color: var(--accent);
  background: var(--card); border: 1px solid var(--line); border-radius: 999px;
  padding: 3px 13px; white-space: nowrap;
}
.discuss-link:hover { border-color: var(--accent); }
h1 { font-size: 30px; line-height: 1.25; margin: 32px 0 8px; letter-spacing: -0.01em; }
h2 { font-size: 22px; margin: 36px 0 8px; }
h3 { font-size: 18px; margin: 28px 0 6px; }
h4 { font-size: 16px; margin: 22px 0 6px; }
.topic-body { max-width: 65ch; overflow-wrap: break-word; }
.question { font-size: 19px; color: var(--muted); font-style: italic; margin: 4px 0 16px; }
.meta-row { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin: 12px 0 24px; }
.badge {
  display: inline-block; font-size: 13px; font-weight: 700; padding: 3px 10px;
  border-radius: 999px; white-space: nowrap;
}
.badge-A { background: #e2f3e5; color: #1c6b2f; }
.badge-B { background: #e0eefb; color: #1d4f8a; }
.badge-C { background: #fdf0dc; color: #8a5a00; }
.badge-D { background: #ececec; color: #555; }
.badge-status { background: var(--amber-bg); color: var(--amber-ink); }
.stamp { font-size: 13px; color: var(--muted); }
a { color: var(--accent); }
.topic-body a { overflow-wrap: anywhere; }
.table-wrap { overflow-x: auto; margin: 16px 0; }
table { border-collapse: collapse; width: 100%; font-size: 15px; }
th, td { border: 1px solid var(--line); padding: 8px 10px; text-align: left; vertical-align: top; }
th { background: var(--accent-soft); }
hr { border: none; border-top: 1px solid var(--line); margin: 32px 0; }
code { background: #f1ede2; padding: 1px 6px; border-radius: 4px; font-size: 0.9em; }
pre { background: #f1ede2; padding: 14px; border-radius: 8px; overflow-x: auto; }
pre code { background: none; padding: 0; }
.chapter { margin-top: 40px; }
.chapter h2 { font-size: 15px; text-transform: uppercase; letter-spacing: 0.06em;
  color: var(--muted); border-bottom: 1px solid var(--line); padding-bottom: 8px; }
.topic-card {
  display: block; background: var(--card); border: 1px solid var(--line);
  border-radius: 12px; padding: 16px 18px; margin: 12px 0;
  text-decoration: none; color: var(--ink);
}
.topic-card:hover { border-color: var(--accent); }
.topic-card h3 { margin: 0 0 4px; font-size: 18px; color: var(--ink); }
.topic-card p { margin: 6px 0 8px; font-size: 15px; color: var(--muted); }
.search-box { margin: 24px 0 8px; }
.search-box input {
  width: 100%; font-size: 17px; padding: 12px 16px; border-radius: 10px;
  border: 1px solid var(--line); background: var(--card); color: var(--ink);
}
.pager { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 12px; margin-top: 48px;
  border-top: 1px solid var(--line); padding-top: 20px; font-size: 15px; }
.pager a { text-decoration: none; }
.pager .next { text-align: right; }
.back-link { display: inline-block; margin-top: 28px; font-size: 15px; text-decoration: none; }
footer.site-footer { border-top: 1px solid var(--line); margin-top: 40px; }
footer.site-footer .wrap { padding-top: 20px; padding-bottom: 40px; font-size: 14px; color: var(--muted); }
.empty-note { color: var(--muted); font-style: italic; }

/* ---- mobile ---- */
@media (max-width: 640px) {
  body { font-size: 16px; }
  .wrap { padding-left: 18px; padding-right: 18px; }
  .site-header .wrap {
    flex-direction: column; align-items: flex-start; gap: 2px;
    padding-top: 10px; padding-bottom: 6px;
  }
  .site-nav { margin-left: 0; flex-wrap: wrap; gap: 0 4px; font-size: 16px; }
  .site-nav a { display: inline-block; padding: 10px 10px 10px 0; margin-right: 8px; }
  .chapter-nav { display: none; }
  .chapter-jump {
    display: block; width: 100%; font-size: 16px; color: var(--ink);
    padding: 12px; margin: 14px 0 4px; border: 1px solid var(--line);
    border-radius: 10px; background: var(--card);
  }
  .discuss-link { padding: 9px 16px; }
  h1 { font-size: 26px; }
  .pager { font-size: 14px; }
}