This circle pack visualization displays the file hierarchy of the React source code, with each circle’s size proportional to file size and color encoding file extension. It uses `d3.pack`, `d3.hierarchy`, and `d3.zoom`, with radial gradients applied to every circle via SVG `<radialGradient>` elements. Gradients are computed from a depth-based grayscale scale for directories and per-extension colors for files. The data loads from a remote Gist, and dynamic recomputation is memoized on DOM nodes using a custom `computed` function.