This heatmap visualizes billionaire wealth across regions and wealth types, with each cell colored by total wealth worth in billions and a tooltip displaying the exact value on hover. The chart uses D3 v6 with SVG rendering, employing `d3.scaleBand` for the x and y axes and `d3.scaleLinear` for the color mapping. Data is loaded from a CSV via `d3.csv`, and interactivity is handled through mouseover, mousemove, and mouseleave events that control a custom tooltip div. The visualization is titled and subtitled directly within the SVG.