This example visualizes the eight counties of Sweden as a choropleth map, with each landmass filled in a light blue color and white internal borders delineating county boundaries. The map uses a Mercator projection fitted to the SVG canvas, with geographic paths generated via `d3.geoPath`. The data is loaded from a TopoJSON file using `d3.json`, then converted into GeoJSON features and a mesh with `topojson.feature` and `topojson.mesh`. The visualization is built with React and D3 v5, rendering all marks as SVG elements.