This example displays a choropleth-style map of Sweden’s counties, highlighting internal boundaries in cyan and county fill in dark blue on a light background. Using React with D3 v5, it loads TopoJSON data from a GitHub gist, converts it to GeoJSON with `topojson.feature`, and renders paths via `d3.geoPath` with a Mercator projection fitted to the viewport. Interior mesh lines are drawn separately using `topojson.mesh`. The visualization updates reactively when data loads.