:root {
  --fg: #1a1a1a;
  --bg: #fdfdfb;
  --accent: #1d4e89;
  --muted: #666;
  --pre-bg: #f3f1ec;
  --border: #e3e0d8;
}

@media (prefers-color-scheme: dark) {
  :root {
    --fg: #ececec;
    --bg: #161616;
    --accent: #6ea8e0;
    --muted: #999;
    --pre-bg: #222;
    --border: #333;
  }
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--fg);
  font-family:
    system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  line-height: 1.55;
}

main {
  max-width: 720px;
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
}

header {
  margin-bottom: 2.5rem;
}

h1 {
  margin: 0 0 0.5rem;
  font-size: 1.85rem;
  letter-spacing: -0.02em;
}

.lede {
  margin: 0;
  color: var(--muted);
  font-size: 1.1rem;
}

section {
  margin-bottom: 2rem;
}

section h2 {
  font-size: 1.15rem;
  border-bottom: 1px solid var(--border);
  padding-bottom: 0.25rem;
  margin-bottom: 0.75rem;
}

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

button {
  font: inherit;
  background: var(--accent);
  color: white;
  border: 0;
  border-radius: 4px;
  padding: 0.5rem 0.9rem;
  cursor: pointer;
}

button:hover {
  filter: brightness(1.1);
}

pre {
  background: var(--pre-bg);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1rem;
  overflow-x: auto;
  white-space: pre-wrap;
  font-size: 0.9rem;
}

.hint {
  margin-top: 0.5rem;
  color: var(--muted);
}

ul, ol {
  padding-left: 1.4rem;
}

footer {
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.9rem;
}