This visualization displays the counties of Sweden as solid black regions with white interior boundaries, rendered using SVG paths generated from TopoJSON data. The map uses a Mercator projection from d3-geo, with `geoPath` and `fitExtent` to scale and position the geometry within the frame. Built with React and D3 v5, the code fetches the Swedish county dataset via `d3.json` from a GitHub Gist, then applies `feature` and `mesh` from TopoJSON to extract boundaries and shared borders. The styling, defined in CSS, gives the map a high-contrast monochrome appearance.