This D3.js v5 pie chart visualizes the Air Quality Index by country, sourced from a CSV file hosted in a GitHub gist. The chart center displays the proportional slices, each colored via the ordinal category-10 color scheme, with a legend on the right listing country names and their corresponding Air Index values. The code uses `d3.pie`, `d3.arc`, and `d3.scaleOrdinal` to generate the slices and layout, and `d3.csv` to load and parse the data. A title, styled with a sans-serif font, appears at the top of the SVG canvas.