A heatmap displays earthquake counts for U.S. states from 2010 to 2015, with color intensity varying by magnitude category. A dropdown menu allows filtering by category range, while hovering over cells reveals exact counts via a tooltip. The visualization uses D3 v5 with SVG rendering, employing `d3.scaleQuantize` for color mapping, `d3.nest` for data grouping, and `d3.csv` to load the dataset.