This example visualizes a small health data network as a force-directed graph, organizing records by gender, then age, and finally metric values for sleep quality and stress level. Nodes are colored by hierarchy level: purple for gender, gold for age, and teal for metric leaves. The layout is computed with `d3.forceSimulation`, using `d3.forceLink`, `d3.forceManyBody`, and `d3.forceCenter`, with draggable nodes via a custom drag handler. Rendering is SVG-based, with node labels and a legend showing the color mapping.