:root {
  --bg: #f2f2f7;
  --text: #1c1c1e;
  --muted: #6c6c70;
  --rule: #d1d1d6;
  --link: #1c1c1e;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #000000;
    --text: #f2f2f7;
    --muted: #98989f;
    --rule: #38383a;
    --link: #f2f2f7;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 17px/1.6 -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", Arial, sans-serif;
  -webkit-text-size-adjust: 100%;
}

main {
  max-width: 640px;
  margin: 0 auto;
  padding: 48px 16px 64px;
}

nav { margin-bottom: 24px; font-size: 15px; }

h1 {
  margin: 0;
  font-size: 34px;
  line-height: 1.15;
  letter-spacing: -0.02em;
}

h2 {
  margin: 36px 0 8px;
  font-size: 20px;
  line-height: 1.3;
}

.meta { margin: 6px 0 0; color: var(--muted); font-size: 15px; }
.lead { margin-top: 24px; font-size: 19px; }

p, ul { margin: 0 0 12px; }
ul { padding-left: 20px; }
li { margin-bottom: 8px; }

a { color: var(--link); text-underline-offset: 3px; }

details {
  border-top: 1px solid var(--rule);
  padding: 12px 0;
}
details:last-of-type { border-bottom: 1px solid var(--rule); }
summary { cursor: pointer; font-weight: 600; }
details p { margin: 8px 0 0; color: var(--muted); }

footer {
  margin-top: 40px;
  font-size: 15px;
  color: var(--muted);
}