This example shows a heatmap of the `heatmap_data.csv` dataset, with each cell colored according to its value using the `d3.scaleSequential` interpolator with the Inferno color scheme. Hovering over a cell triggers a tooltip that displays the exact value of that cell, implemented via mouse events and the `d3.select` API. The SVG rendering includes axes built with `d3.axisBottom` and `d3.axisLeft`, and the tooltip's position is set using `d3.mouse`.