A pie chart displays the top ten most populous countries in 2020, with each slice sized by population and a legend listing each country alongside its population in millions. The visualization loads CSV data from a GitHub gist via `d3.csv`, then uses `d3.pie` and `d3.arc` to generate SVG paths, with `d3.scaleOrdinal` assigning a distinct color to each slice. A separate legend group renders colored rectangles and text labels using `d3.select` and data joins, while `d3.format` converts raw numbers into readable millions values.