This example shows the Old Faithful dataset as a 2D heatmap, binning eruption duration versus waiting time and coloring cell counts with a green scheme. It uses Vega-Lite’s specification API to define the chart, with `d3.tsv` loading the data. A mousemove listener updates the chart by re-rendering with new maximum bin counts based on the cursor’s x position. The code leverages `vegaEmbed` to render the visualization as SVG.