This choropleth map visualizes deaths from brain and central nervous system cancer across countries for 2019, using a yellow-to-red sequential color scale to encode mortality counts. The visualization renders world geography with `d3.geoNaturalEarth1` and `d3.geoPath`, combining TopoJSON country boundaries from the World Atlas with CSV health data joined via country codes. React manages interactive state, while D3’s `scaleSequential` with `interpolateYlOrRd` drives the color encoding. Hovering over a country displays its name and total deaths in a floating toolkit, and a legend shows the scale’s domain.