This interactive visualization displays a collapsible tree of programming languages organized across four layers: root, paradigm, family, and language. Using D3 v7’s `d3.hierarchy` and `d3.tree` layouts, nodes render as distinct SVG symbols (star, triangle, square, circle) with colors varying by depth. Clicking nodes collapses or expands branches, with `transition` animations smoothly redrawing link paths and node positions. The initial view collapses nodes at depth ≥2, showing only paradigms and families until expanded.