:root {
  color-scheme: light;
  --bg: #ffffff;
  --paper: #ffffff;
  --ink: #111111;
  --muted: #555555;
  --line: #e5e5e5;
  --accent: #111111;
  --accent-dark: #111111;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: ui-serif, "Songti SC", "Noto Serif CJK SC", Georgia, serif;
  line-height: 1.78;
}

a {
  color: var(--accent-dark);
}

.shell {
  width: min(920px, calc(100% - 32px));
  margin: 0 auto;
  padding: 56px 0 72px;
}

.topbar {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: center;
  margin-bottom: 42px;
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 14px;
}

.brand {
  color: var(--ink);
  font-weight: 700;
  letter-spacing: 0.04em;
}

.nav {
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
}

.paper {
  background: var(--paper);
  border: 1px solid var(--line);
  box-shadow: none;
  padding: clamp(28px, 6vw, 64px);
}

.eyebrow {
  color: var(--accent-dark);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

h1 {
  margin: 12px 0 10px;
  font-size: clamp(34px, 7vw, 64px);
  line-height: 1.04;
  letter-spacing: 0;
}

.summary {
  max-width: 720px;
  margin: 0 0 34px;
  color: #333333;
  font-size: 18px;
}

.meta {
  display: grid;
  gap: 8px;
  margin: 0 0 34px;
  padding: 18px 20px;
  border: 1px solid var(--line);
  background: #fafafa;
  color: #333333;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 14px;
}

.toc {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 10px 18px;
  margin: 0 0 40px;
  padding: 22px;
  border: 1px solid var(--line);
  background: #ffffff;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 14px;
}

h2 {
  margin: 36px 0 12px;
  padding-top: 6px;
  font-size: 24px;
  line-height: 1.3;
}

p,
li {
  font-size: 16px;
}

ul {
  padding-left: 1.25em;
}

.note {
  margin-top: 38px;
  padding: 18px 20px;
  border-left: 4px solid var(--accent);
  background: #fafafa;
  color: #333333;
}

.footer {
  margin-top: 28px;
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 13px;
}

@media (max-width: 640px) {
  .shell {
    width: min(100% - 24px, 920px);
    padding: 28px 0 48px;
  }

  .topbar {
    align-items: flex-start;
    flex-direction: column;
  }

  .paper {
    padding: 24px 18px;
  }
}