This choropleth map of Croatia displays population density by county, using a red sequential color scale with a corresponding legend. Each county shape is colored based on its density class, and hovering over a region reveals a tooltip with the county name, population, and density. Built with D3 v6, the visualization loads geographic data from a TopoJSON file, projects it using `d3.geoMercator`, and renders paths via `d3.geoPath`.