This example shows a hierarchical tree of programming languages organized by paradigm, with four levels from root to leaf. It uses D3 v7’s `d3.hierarchy` and `d3.tree` layout with an SVG rendering approach, drawing horizontal links via `d3.linkHorizontal`. Nodes appear as blue circles with labels, and the layout adapts to an 800px-high viewBox, though the CSS height also adjusts to the viewport.