This visualization tracks cumulative COVID-19 death counts across multiple countries over time, using a multi-line chart that plots deaths against days since the first reported case. The chart includes a draggable vertical line that, when positioned at a specific day, reveals the death toll for each country at that point in time. The code uses D3 v5 APIs including `nest()`, `scaleLinear`, and `line` with `curveBasis` to generate the paths, while a custom `colorLegend` module displays the categorical color scale using `scaleOrdinal` and `schemeCategory10`. Data comes from the included CSV files `data01.csv` and `data02.csv`.