:root {
  --max-width: 720px;
  --color-text: #1a1a1a;
  --color-muted: #5a5a5a;
  --color-link: #0b5fb3;
  --color-rule: #e3e3e3;
  --color-callout-bg: #f5f7fa;
  --color-callout-border: #0b5fb3;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, sans-serif;
  font-size: 17px;
  line-height: 1.6;
  color: var(--color-text);
  margin: 0;
  padding: 2.5rem 1.25rem;
  background: #fff;
}

main {
  max-width: var(--max-width);
  margin: 0 auto;
}

h1 {
  font-size: 2rem;
  margin: 0 0 0.25rem;
  line-height: 1.25;
}

h2 {
  font-size: 1.35rem;
  margin: 2.5rem 0 0.5rem;
  line-height: 1.3;
}

h3 {
  font-size: 1.1rem;
  margin: 1.75rem 0 0.5rem;
}

p { margin: 0.75rem 0; }

.subtitle {
  color: var(--color-muted);
  margin: 0 0 2rem;
  font-size: 1.05rem;
}

a { color: var(--color-link); }
a:hover { text-decoration: underline; }

ul, ol { padding-left: 1.5rem; }
li { margin-bottom: 0.35rem; }

dl { margin: 1rem 0; }
dl dt { font-weight: 600; margin-top: 0.85rem; }
dl dd { margin: 0.15rem 0 0 0; }

.callout {
  background: var(--color-callout-bg);
  border-left: 3px solid var(--color-callout-border);
  padding: 1rem 1.25rem;
  margin: 1.5rem 0;
}

.callout p { margin: 0; }

footer {
  margin-top: 4rem;
  padding-top: 1rem;
  border-top: 1px solid var(--color-rule);
  color: var(--color-muted);
  font-size: 0.9rem;
}

footer p { margin: 0.4rem 0; }

nav.crumbs {
  font-size: 0.9rem;
  margin-bottom: 1.5rem;
  color: var(--color-muted);
}

@media (max-width: 480px) {
  body { padding: 1.5rem 1rem; font-size: 16px; }
  h1 { font-size: 1.65rem; }
  h2 { font-size: 1.2rem; }
}