*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.6;
  color: #1a1a1a;
  max-width: 680px;
  margin: 0 auto;
  padding: 2rem 1rem;
}
h1 { font-size: 1.8rem; margin-bottom: 0.5rem; }
h2 { font-size: 1.3rem; margin-top: 1.5rem; margin-bottom: 0.5rem; }
p, ul, ol { margin-bottom: 1rem; }
ul, ol { padding-left: 1.5rem; }
a { color: #0066cc; }
nav { margin-bottom: 2rem; font-size: 0.9rem; }
nav a { margin-right: 1rem; }
footer { margin-top: 3rem; padding-top: 1rem; border-top: 1px solid #ddd; font-size: 0.85rem; color: #666; }
code { background: #f4f4f4; padding: 0.1em 0.3em; border-radius: 3px; font-size: 0.9em; }