This interactive visualization displays a collapsible hierarchical tree of the Flare software package’s class structure. Users click nodes to expand or collapse branches, with smooth transitions animating the tree’s layout changes. The visualization uses d3.hierarchy and d3.tree to compute node positions, d3.linkHorizontal for curved links, and d3.zoom for panning and scaling. Data comes from flare-2.json, rendered as SVG elements with circles and labels, updating via enter, update, and exit selections with d3.transition.