This visualization displays projected population changes from 1950 to 2100 for global regions, with each line color-coded by region and sorted by final population size. A vertical line marks the currently selected year, which users can change by moving the mouse across the chart. The code uses D3 v5 APIs including `scaleTime`, `scaleLinear`, `nest`, `line` with `curveBasis`, `axisBottom`, and `axisLeft` to render the SVG. Data comes from two UN population estimate CSV files, merged and melted into yearly observations for each region.