This example renders a choropleth map of Indian states using D3.js v5 and TopoJSON, with a Mercator projection and SVG paths generated via `d3.geoPath`. Each state is filled with a categorical color from `d3.scaleOrdinal` and labeled with its name at the path centroid. Clicking a state toggles its fill color between the original and a brighter white-blended version using `d3.interpolateRgb`. State boundaries are styled with a white stroke, and the map is layered over a yellow SVG background.