This example displays a map of England with its geographical regions highlighted in green and internal boundaries in yellow. Built with React and D3 v7, it uses `d3.geoNaturalEarth1` for projection and `d3.geoPath` to render TopoJSON features. The data is loaded from a GitHub gist via `d3.json` and processed with the `topojson` library’s `feature` and `mesh` functions. The visualization renders as an SVG, with the `Marks` component generating styled path elements for each region and interior border.