:root {
  --bg: #f3f4f6;
  --card: #ffffff;
  --text: #111827;
  --muted: #6b7280;
  --border: #e5e7eb;
  --link: #2563eb;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto,
    "Noto Sans CJK SC", "Noto Sans SC", "PingFang SC", "Microsoft YaHei",
    Arial, sans-serif;
  line-height: 1.7;
}

a { color: var(--link); text-decoration: none; }

a:hover { text-decoration: underline; }

.wrap {
  max-width: 920px;
  margin: 0 auto;
  padding: 24px 16px 56px;
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 12px;
  flex-wrap: wrap;
  margin-bottom: 14px;
}

.back {
  color: var(--muted);
  font-size: 14px;
}

.back a { color: var(--muted); }

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 18px 16px;
  box-shadow: 0 1px 2px rgba(0,0,0,.04);
}

.card + .card { margin-top: 14px; }

h1 { font-size: 22px; margin: 0; }

h2 { font-size: 18px; margin: 0 0 10px; }

h3 { font-size: 16px; margin: 14px 0 8px; }

h4 { font-size: 15px; margin: 14px 0 8px; }

p { margin: 10px 0 0; }

ul, ol { margin: 10px 0 0; padding-left: 20px; }

li { margin: 6px 0; }

img {
  max-width: 100%;
  height: auto;
  display: block;
  border: 1px solid var(--border);
  border-radius: 12px;
  margin-top: 8px;
}

code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas,
    "Liberation Mono", "Courier New", monospace;
  font-size: 0.95em;
  background: #f9fafb;
  border: 1px solid var(--border);
  padding: 0 6px;
  border-radius: 8px;
}