This visualization presents the Old Faithful dataset as a binned heatmap, with eruption duration on the x-axis and waiting time on the y-axis, colored by the mean waiting time within each bin using a green color scheme. The code builds the chart through Vega-Lite’s layered API, combining rect marks for the heatmap cells and text marks to label each bin’s average value, while vegaEmbed renders the final SVG. Data is loaded via d3.tsv from the raw GitHub source, and the bin count is fixed at 10 along the horizontal axis.