A line chart tracks cumulative global COVID-19 deaths over time using a timeline from the Johns Hopkins dataset, with a horizontal marker line at 500,000 deaths and a vertical marker labeled "now" at the most recent date. The React component builds a D3 v5 `scaleTime` and `scaleLinear` to map dates and totals, then uses a `line` generator to draw the SVG path. Custom `YMarkerLine` and `XMarkerLine` components render the threshold and current-date annotations, emphasizing the crossing of the half-million milestone.