This example displays a choropleth map of Mexico’s regions, rendered as SVG paths using a Mercator projection. The code loads TopoJSON data from a gist, converts it to GeoJSON with `topojson.feature`, and draws each region via `d3.geoPath`. The visualization layers graticule lines and land borders, with CSS styling assigning distinct colors to the land, graticules, and regional boundaries. The map is built in React using `useState` and `useEffect` to fetch and prepare the data, then renders the marks through a custom `Marks` component.