This choropleth map colors world countries by income group, using a spectral color scale with an accompanying legend. The visualization is built with D3.js, using `d3.geoPath` and `d3.geoNaturalEarth1` for map projection and rendering, and `zooming` via `d3.zoom` event handling. Country data comes from the `world-atlas` package, with income group information joined from a TSV file, and the map supports hover highlighting.