This example visualizes global COVID-19 death counts over time as a line chart, with marker lines highlighting the latest date on the x-axis and the 500 million death threshold on the y-axis. The chart is built using React and renders SVG elements directly. It loads data from a CSV file using `d3.csv` and applies `d3.scaleTime` and `d3.scaleLinear` for scaling. Custom `XMarkerLine` and `YMarkerLine` components, using `d3.timeFormat` and `d3.format`, add annotated guide lines, while the x-axis uses `d3.axisBottom` for ticks and grid lines.