This choropleth map visualizes brain and central nervous system cancer deaths for countries in 2019, using a yellow-to-red sequential color scale from D3’s `scaleSequential` and `interpolateYlOrRd`. The map renders with `geoNaturalEarth1`, `geoPath`, and TopoJSON world-atlas data. Hovering over a country reveals its name and total deaths via a tooltip appended with D3’s `select`. React manages state and lifecycle, loading CSV data from two external sources, while a static legend at the left encodes death-count ranges.