A vertical hierarchy visualization shows a four-layer taxonomy of programming languages, from root to paradigm, language, and feature levels. The flat parent-child array is converted to a tree structure using `d3.stratify()`, then positioned with `d3.tree()`. Each depth layer receives a distinct color and node radius, and curved links are drawn with `d3.linkVertical()`. The SVG renders with bounding-box computation for dynamic viewBox sizing.