A choropleth map of Croatian counties displays population density using a red sequential color scale, with a legend categorizing density ranges and hover tooltips showing county name, population, and density. The visualization loads TopoJSON data from `Croatia.json` and renders it as SVG paths using `d3.geoPath` with a `geoMercator` projection. The code styles each county by its density class via `d3.scaleLinear` and `schemeReds[9]`, while `d3.scaleOrdinal` powers the legend; the map lacks zoom interactivity despite commented-out `d3.zoom` code.