This interactive collapsible tree visualization displays a hierarchical dataset of the Flare visualization library codebase, with nodes representing packages and functions. Built with D3 v6, it renders as an SVG with animated transitions that reposition nodes and links when a node is clicked to expand or collapse its children, using a horizontal diagonal link layout. The implementation relies on `d3.tree()` for layout, `d3.linkHorizontal()` for edges, `d3.select()` for SVG manipulation, and `d3.transition()` for smooth 250ms animations. The tree data comes from the `flare-2.json` file, and nodes with names shorter than seven characters are initially collapsed.