A hierarchical sunburst chart displays hierarchical data as concentric rings of arcs, with colors assigned to top-level branches. Clicking a segment smoothly zooms and re-centers the visualization on that arc, expanding its children outward while fading unrelated elements. Built with D3 v5, it loads data via the Observable standard library and uses `d3.hierarchy`, `d3.partition`, and `d3.arc` to compute and render the layout as SVG. Interactive transitions rely on `transition.attrTween` and `d3.interpolate` to animate arc positions and label rotations.