A choropleth map of world countries colored by economic group, with an interactive color legend that filters the map. Hovering reveals a country’s name and value via a `title` tooltip, while clicking a legend tick toggles highlighting of that category and dims others. Built with D3 v5, it uses `geoNaturalEarth1` projection with `geoPath`, `scaleOrdinal` and `schemeSpectral`, `zoom` for panning, and `topojson.feature` to load world-atlas data.