This example visualizes the total Grand Slam titles won by tennis’s “Big Three” as an indented tree diagram. Node circles are sized by each player’s slam count, showing the hierarchy of players and their titles. The code uses the D3.js v7 library to load and stratify a CSV from a GitHub gist, then applies `d3.tree` to compute the layout. The resulting SVG is rendered with cubic Bézier links and labeled nodes, with circles sized by the `value` field.