This choropleth map visualizes global population data using a Mercator projection and color-encoded country values. D3 v7 loads GeoJSON world boundaries and CSV population data via `Promise.all`, then applies a sequential `d3.scaleSequential` with an `interpolateYlGnBu` color scheme. The code uses `d3.geoPath` and `d3.geoMercator` to render SVG paths, and displays a linear gradient legend with an axis. Countries lacking population data render in gray, while hover tooltips provide country names and values.