body { font-family: system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", sans-serif; max-width: 640px; margin: 48px auto; padding: 0 20px; line-height: 1.7; color: #222; }
h1 { font-size: 28px; margin-bottom: 4px; }
h2 { font-size: 18px; margin-top: 28px; }
a { color: #0969da; }
footer { margin-top: 40px; color: #888; font-size: 13px; }