This example visualizes the counties of Sweden as a choropleth map, using a red fill for each county and yellow lines to highlight interior borders. The map is rendered as an SVG using React, with geographic data from a remote TopoJSON file. The code employs `topojson.feature` and `topojson.mesh` to extract county boundaries and interior edges, and `d3.geoPath` with the Mercator projection to project the geometries. The projection is fitted to the map's extent using `fitExtent`.