This chart displays cumulative COVID-19 deaths over time for multiple countries, using a line chart where hovering over any point highlights the corresponding country's entire trajectory and displays a tooltip with the country name, death count, and date. The implementation uses React with D3 v7 scales, line generators, and axes, while a Voronoi overlay built with `d3.Delaunay` captures mouse events across the entire plot area for precise hover detection. Data comes from the CSSEGISandData COVID-19 time series dataset, with the active line emphasized in black and labeled via SVG text elements.