:root {
  --paper: #f4f1ea;
  --paper-soft: #ece8dc;
  --ink: #1a1a1a;
  --ink-soft: #55524b;
  --ink-faded: #8f8b80;
  --seal: #b4281e;
  --rule: #1a1a1a;
  --serif: 'Songti SC', 'STSong', 'Source Han Serif CN', 'Noto Serif CJK SC', 'SimSun', Georgia, 'Times New Roman', serif;
  --serif-en: 'Iowan Old Style', 'Palatino Linotype', 'Book Antiqua', Georgia, 'Times New Roman', serif;
  --sans: 'PingFang SC', 'Microsoft YaHei', 'Hiragino Sans GB', system-ui, -apple-system, sans-serif;
  --sans-en: 'Avenir Next', 'Segoe UI', 'Helvetica Neue', Helvetica, Arial, sans-serif;
  --mono: 'SF Mono', Menlo, Monaco, Consolas, 'Courier New', monospace;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: var(--sans);
  line-height: 1.7;
  color: var(--ink);
  background: var(--paper);
}

body.lang-en {
  font-family: var(--sans-en);
  letter-spacing: 0.01em;
}

a { color: var(--seal); }

.wrap {
  max-width: 860px;
  margin: 0 auto;
  padding: 40px 24px 72px;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 28px;
}

.back {
  display: inline-block;
  color: var(--seal);
  text-decoration: none;
  font-family: var(--mono);
  font-size: 13px;
}

.lang-switch {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 10px;
  border: 1px solid rgba(26, 26, 26, 0.16);
  border-radius: 999px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-faded);
}

.lang-switch a {
  color: var(--ink-faded);
  text-decoration: none;
}

.lang-switch a.active {
  color: var(--ink);
}

h1, h2 {
  font-family: var(--serif);
  font-weight: 500;
  line-height: 1.2;
}

body.lang-en h1,
body.lang-en h2 {
  font-family: var(--serif-en);
}

h1 {
  margin: 0 0 12px;
  font-size: 42px;
}

h2 {
  margin: 36px 0 12px;
  font-size: 24px;
  border-top: 1px solid var(--rule);
  padding-top: 20px;
}

p, li {
  color: var(--ink-soft);
  font-size: 16px;
}

ul {
  padding-left: 20px;
}

.meta {
  color: var(--ink-soft);
  font-family: var(--mono);
  font-size: 13px;
}

code {
  font-family: var(--mono);
  background: var(--paper-soft);
  padding: 2px 6px;
  border-radius: 4px;
}

@media (max-width: 720px) {
  .topbar {
    flex-direction: column;
    align-items: flex-start;
  }

  h1 {
    font-size: 34px;
  }
}