:root { color-scheme: light; font: 15px/1.5 system-ui, sans-serif; color: #172436; background: #fff; }
body { margin: 0; }
main { max-width: 480px; margin: auto; padding: 20px 12px; }
.diagram { display: block; width: 100%; height: auto; }
nav { display: flex; flex-wrap: wrap; gap: 8px 20px; padding: 8px 24px; }
a { color: #1d4ed8; text-underline-offset: .2em; }
a:focus-visible { outline: 3px solid #1d4ed8; outline-offset: 5px; }