This choropleth map visualizes countries by income group, using color to encode each nation's categorical data. The map shows the geographical distribution of these groups across the world, with a color legend positioned on the left. It is built with D3 v5, using `d3.geoPath` with a `geoNaturalEarth1` projection to render world shapes from TopoJSON data loaded via the `world-atlas` package, which also provides TSV metadata for country names and income groups. A `scaleOrdinal` with a spectral color scheme drives the fill, while zooming and hover effects enhance interaction.