Map with Selectable Countries
This example presents an interactive choropleth map of world countries colored by economic classification. Users can click countries to highlight them while dimming all others, and clicking again deselects. The visualization also includes a clickable color legend that filters which categories remain visible. Built with D3 v5, it uses `d3.geoNaturalEarth1`, `d3.geoPath`, and `d3.zoom` for map rendering and interaction, while the color scale uses `d3.scaleOrdinal` with `d3.schemeSpectral`. Country boundaries and names come from TopoJSON world-atlas data.