A choropleth map colors world countries by economy category using an ordinal color scale, with a color legend that filters to a single category when clicked. The map and legend are built with D3 v5, using `d3.geoNaturalEarth1` and `d3.geoPath` for projection and rendering, and `d3.zoom` for pan and zoom. Data comes from the World Atlas TopoJSON and TSV files, loaded with `d3.json` and `d3.tsv`, and countries are highlighted or dimmed based on the selected color value.