The visualization animates daily COVID-19 mortality and case averages across the United States using NYT rolling-averages data. A reusable D3 scatter plot framework, built with `scaleTime`, `scaleLinear`, and `axisBottom`, transitions circles smoothly between the two metrics every 2.4 seconds. The SVG rendering displays month and year tick labels, a y-axis label, and a vaccination milestone annotation. It uses `selectAll`, `data().join()`, and `transition().delay()` to update positions and redraw axes.