body { font-family: system-ui, sans-serif; line-height: 1.6; color: #222; background: #fff; margin: 0; }
main { max-width: 720px; margin: 0 auto; padding: 16px; }
h1 { font-size: 1.6rem; }
h2 { font-size: 1.2rem; margin-top: 1.5rem; }
a { color: #b3261e; }
.nhap { background: #fff3cd; padding: 8px 12px; border-radius: 6px; }
@media (prefers-color-scheme: dark) {
  body { color: #eee; background: #121212; }
  a { color: #ffb4ab; }
  .nhap { background: #4d3d00; }
}