This example shows a global choropleth map of average annual temperatures by country, with selected nations colored from blue (cold) to red (hot) and unlisted countries in gray. It uses d3.json to load TopoJSON world boundaries via topojson.feature, then d3.geoPath with a geoNaturalEarth1 projection to render SVG paths. A d3.scaleSequential with d3.interpolateRdYlBu encodes temperature values, while a linear-gradient legend and browser tooltip titles provide context from a hardcoded dataset.