This visualization displays a map of Swedish counties using a Mercator projection, with the counties filled in teal and their borders drawn in a complementary green. The code loads GeoJSON data via `d3.json`, processes it with the TopoJSON `feature` and `mesh` functions to extract county geometries and interior boundaries, and renders them as SVG paths using `d3.geoPath` within a React component. The map is fitted to the viewport, and the styling is applied through CSS classes.