This example shows a pie chart of product sales aggregated by category, with animated slices that grow into place using a transition. It uses D3.js v7 to load data from a CSV file hosted on GitHub Gist, aggregate sales with `d3.rollup`, and generate pie slices via `d3.pie` and `d3.arc`. Labels are placed outside the slices with connecting polylines, and a legend is appended. The animation relies on `transition.attrTween` with an interpolated arc.