This example shows a world map where each country is colored according to its income group, using a spectral color scale. Users can pan and zoom the map, and hovering over a country displays its name and income group in a tooltip. The visualization is rendered with SVG and uses d3.geoNaturalEarth1 for the projection, d3.geoPath for drawing country boundaries, and d3.zoom for interactivity. Data is loaded from TopoJSON and TSV files via the world-atlas package, with income data from a CSV file.