This example shows a hierarchical circle-packing layout of the Flare software package’s class hierarchy, with each node’s size proportional to its value and color mapped to depth. Using D3 v4’s `d3.stratify` to build the hierarchy from CSV data and `d3.pack` for layout, circles are rendered as SVG groups. Interactivity highlights all ancestor circles on hover via the `d3.selectAll` and `classed` methods, while leaf labels are clipped to their circles.