This example shows a static tree diagram generated by D3 v4, laying out a small binary hierarchy of nodes and links with `d3.tree()` and `d3.hierarchy()`. The visualization renders in an SVG using `d3.linkHorizontal()` for curved paths and circle-plus-text labels for each node. The code builds the tree data programmatically from a root object, assigns positions via `tree(root)`, and applies transform translation to group elements for placement.