:root {
  --bg: #ffffff;
  --bg-soft: #f6f8fa;
  --bg-card: #ffffff;
  --line: #d8dee4;
  --line-soft: #eaeef2;
  --ink: #1f2328;
  --ink-2: #57606a;
  --ink-3: #8b949e;
  --accent: #1f6feb;
  --accent-soft: #ddf4ff;
  --src: #1a7f37;
  --src-soft: #dafbe1;
  --lec: #8250df;
  --lec-soft: #fbefff;
  --warn: #9a6700;
  --shadow: 0 1px 3px rgba(31, 35, 40, .09), 0 6px 22px rgba(31, 35, 40, .06);
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg-soft);
  color: var(--ink);
  font: 15px/1.75 -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei",
        "PingFang SC", "Hiragino Sans GB", "Source Han Sans SC", sans-serif;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 40;
  display: flex; align-items: center; gap: 14px;
  height: 52px; padding: 0 18px;
  background: rgba(255,255,255,.88);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--line);
}
.topbar .brand { font-weight: 700; font-size: 14.5px; letter-spacing: .2px; white-space: nowrap; }
.topbar .brand span { color: var(--ink-3); font-weight: 500; }
.topbar .crumbs { display: flex; gap: 6px; align-items: center; flex: 1; min-width: 0;
  font-size: 13px; color: var(--ink-2); overflow: hidden; white-space: nowrap; }
.topbar .crumbs a { color: var(--ink-2); }
.topbar .crumbs .sep { color: var(--ink-3); }
.topbar .acts { display: flex; gap: 8px; }
.tbtn {
  font: inherit; font-size: 12.5px; padding: 5px 11px; cursor: pointer;
  border: 1px solid var(--line); border-radius: 7px; background: #fff; color: var(--ink-2);
  white-space: nowrap;
}
.tbtn:hover { border-color: var(--accent); color: var(--accent); }

/* ---------- layout ---------- */
.wrap { display: grid; grid-template-columns: 268px minmax(0, 1fr); }
.side {
  position: sticky; top: 52px; align-self: start;
  height: calc(100vh - 52px); overflow: auto;
  padding: 16px 10px 40px 16px;
  border-right: 1px solid var(--line);
  background: #fff;
  font-size: 13.5px;
}
.side h3 { margin: 16px 6px 6px; font-size: 11.5px; letter-spacing: .8px; color: var(--ink-3);
  text-transform: uppercase; font-weight: 700; }
.side ul { list-style: none; margin: 0; padding: 0; }
.side li { margin: 0; }
.side a {
  display: block; padding: 5px 9px; border-radius: 6px; color: var(--ink-2);
  line-height: 1.45;
}
.side a:hover { background: var(--bg-soft); text-decoration: none; }
.side a.on { background: var(--accent-soft); color: #0a3069; font-weight: 600; }
.side .lv2 a { padding-left: 20px; }
.side .lv3 a { padding-left: 34px; font-size: 13px; }
.side .lv4 a { padding-left: 46px; font-size: 12.5px; color: var(--ink-3); }
.side .pill { font-size: 10.5px; color: var(--ink-3); padding: 0 4px; }

main { padding: 26px 34px 90px; min-width: 0; }
.card {
  background: var(--bg-card); border: 1px solid var(--line-soft); border-radius: 14px;
  box-shadow: var(--shadow); margin-bottom: 22px; overflow: hidden;
}
.card-h {
  display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap;
  padding: 16px 22px 12px; border-bottom: 1px solid var(--line-soft);
}
.card-h h2 { margin: 0; font-size: 15px; letter-spacing: .3px; }
.card-h .hint { font-size: 12.5px; color: var(--ink-3); }
.card-b { padding: 16px 22px 20px; }

/* ---------- hero ---------- */
.hero { padding: 22px 24px 20px; }
.hero .kicker { font-size: 12px; letter-spacing: 1.6px; color: var(--accent); font-weight: 700; }
.hero h1 { margin: 6px 0 10px; font-size: 27px; line-height: 1.35; letter-spacing: .4px; }
.hero .lead { margin: 0; color: var(--ink-2); font-size: 15px; max-width: 60em; }

/* ---------- chips ---------- */
.chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 14px; }
.chip {
  display: inline-flex; align-items: center; gap: 6px;
  font-size: 12.5px; padding: 4px 10px; border-radius: 999px;
  border: 1px solid var(--line); background: #fff; color: var(--ink-2);
}
.chip b { font-weight: 600; color: var(--ink); }
.chip.src { border-color: #a3d8b0; background: var(--src-soft); color: #0f5323; }
.chip.lec { border-color: #d8c2f7; background: var(--lec-soft); color: #4c2889; }
.chip.nav { cursor: pointer; }
.chip.nav:hover { border-color: var(--accent); color: var(--accent); }

/* ---------- mind map ---------- */
.mm-shell { position: relative; background: #fbfcfd; }
.mm-fixed .mm-shell { height: calc(100vh - 190px); min-height: 420px; }
.mm-shell svg { display: block; width: 100%; height: 100%; cursor: grab; user-select: none; }
.mm-tools {
  position: absolute; right: 12px; bottom: 12px; display: flex; gap: 6px;
  background: rgba(255,255,255,.94); padding: 5px; border-radius: 9px;
  border: 1px solid var(--line); box-shadow: var(--shadow);
}
.mm-tools button {
  font: inherit; font-size: 12px; min-width: 30px; height: 26px; cursor: pointer;
  border: 1px solid transparent; border-radius: 6px; background: #fff; color: var(--ink-2);
}
.mm-tools button:hover { background: var(--bg-soft); color: var(--accent); }
.mm-tools .zoom { font-size: 11.5px; color: var(--ink-3); display: flex; align-items: center; padding: 0 4px; }
.mm-legend {
  display: flex; gap: 16px; flex-wrap: wrap; padding: 9px 16px;
  font-size: 12px; color: var(--ink-3); border-top: 1px solid var(--line-soft); background: #fff;
}
.mm-legend i { display: inline-block; width: 11px; height: 11px; border-radius: 3px; margin-right: 5px;
  vertical-align: -1px; }
.mm-legend .k1 { background: #0d2a52; }
.mm-legend .k2 { background: #f6f8fa; border: 1.6px solid #2f81f7; }
.mm-legend .k3 { background: #fff; border: 1px dashed #57606a; }
.mm-legend .k4 { background: #1f6feb; border-radius: 50%; }

/* ---------- body prose ---------- */
.prose { font-size: 15.5px; }
.prose > *:first-child { margin-top: 0; }
.prose h2 {
  font-size: 17px; margin: 30px 0 10px; padding-bottom: 7px;
  border-bottom: 1px solid var(--line-soft);
}
.prose h3 { font-size: 15.5px; margin: 22px 0 8px; }
.prose p { margin: 10px 0; }
.prose ul, .prose ol { margin: 10px 0; padding-left: 24px; }
.prose li { margin: 5px 0; }
.prose blockquote {
  margin: 14px 0; padding: 11px 16px; border-left: 3px solid var(--src);
  background: #fbfdfc; color: #24312a; border-radius: 0 8px 8px 0; font-size: 14.8px;
}
.prose blockquote p { margin: 4px 0; }
.prose blockquote .cite {
  display: block; margin-top: 6px; font-size: 12.5px; color: var(--src); font-style: normal;
}
.prose blockquote .cite a { color: var(--src); border-bottom: 1px dotted var(--src); }
.prose table { border-collapse: collapse; width: 100%; margin: 14px 0; font-size: 14.2px; }
.prose th, .prose td { border: 1px solid var(--line); padding: 8px 11px; text-align: left; vertical-align: top; }
.prose th { background: var(--bg-soft); font-weight: 600; }
.prose code { font-family: var(--mono); font-size: 13px; background: var(--bg-soft);
  padding: 1px 5px; border-radius: 4px; }
.prose strong { font-weight: 650; }
.prose hr { border: 0; border-top: 1px solid var(--line-soft); margin: 26px 0; }

/* ---------- neighbours / sources / backlinks ---------- */
.grid2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); gap: 18px; }
.nb { display: flex; flex-direction: column; gap: 3px; padding: 9px 12px; border-radius: 9px;
  border: 1px solid var(--line-soft); background: #fff; margin-bottom: 7px; }
.nb:hover { border-color: var(--accent); text-decoration: none; }
.nb .t { font-size: 14px; color: var(--ink); font-weight: 550; }
.nb .m { font-size: 12px; color: var(--ink-3); }
.nb .m .pg { color: var(--src); }

.pglist { display: flex; flex-wrap: wrap; gap: 7px; }
.pglink {
  display: inline-flex; align-items: center; gap: 6px; padding: 5px 10px; border-radius: 8px;
  background: var(--src-soft); color: #0f5323; font-size: 13px; border: 1px solid #a3d8b0;
}
.pglink:hover { text-decoration: none; background: #c6f0d2; }
.pglink .lab { font-weight: 650; }
.pglink.lec { background: var(--lec-soft); color: #4c2889; border-color: #d8c2f7; }
.pglink.lec:hover { background: #f3e6ff; }

.empty { font-size: 13px; color: var(--ink-3); padding: 6px 0; }
.bl-item { padding: 8px 0; border-bottom: 1px dashed var(--line-soft); font-size: 14px; }
.bl-item:last-child { border-bottom: 0; }
.bl-item .ctx { font-size: 12.5px; color: var(--ink-3); margin-top: 2px; }

/* ---------- source reader ---------- */
.reader-bar {
  display: flex; align-items: center; gap: 10px; flex-wrap: wrap;
  padding: 12px 22px; border-bottom: 1px solid var(--line-soft); background: #fff;
}
.reader-bar .title { font-weight: 650; font-size: 15px; }
.reader-bar .spacer { flex: 1; }
.mark { background: #fff8c5; border-radius: 3px; padding: 1px 2px; box-shadow: 0 0 0 1px #f5e27a inset; }
.jump-note { font-size: 12.5px; color: var(--ink-3); padding: 8px 22px; background: #fcfdfe;
  border-bottom: 1px solid var(--line-soft); }
.pages { padding: 6px 22px 30px; }
.page { padding: 16px 0; border-bottom: 1px solid var(--line-soft); scroll-margin-top: 110px; }
.page:last-child { border-bottom: 0; }
.page:target { background: #fffdf0; }
.page-h { display: flex; align-items: center; gap: 10px; margin-bottom: 8px; }
.page-h .no {
  font: 600 12px/1 var(--mono); color: #0f5323; background: var(--src-soft);
  border: 1px solid #a3d8b0; padding: 4px 7px; border-radius: 6px;
}
.page-h .no.lec { color: #4c2889; background: var(--lec-soft); border-color: #d8c2f7; }
.page-h .ln { font-size: 12px; color: var(--ink-3); }
.page-h .spacer { flex: 1; }
.page-body { font-size: 14.6px; line-height: 1.95; color: #24292f; white-space: pre-wrap; }
.page-body.ocr { font-family: var(--mono); font-size: 13.6px; }

@media (max-width: 900px) {
  .wrap { grid-template-columns: 1fr; }
  .side { display: none; }
  main { padding: 18px 14px 60px; }
}