This example visualizes the global spread of COVID-19 cases on a date in August 2020, plotting semi-transparent red circles on a natural Earth projection map. Circle size encodes case counts using a square-root scale, while hover tooltips show country names and totals. Built with React and D3 v5, it uses `d3.geoNaturalEarth1`, `d3.geoPath`, `d3.geoCentroid`, and `d3.zoom` for navigation, with TopoJSON world data and CSV time-series data from a COVID-19 repository. Custom legends display color and size scales via `d3.scaleOrdinal` and `d3.scaleSqrt`.