This example shows population trends over time for world regions, with each region drawn as a colored line against year and population axes. A color legend on the right identifies each region, and the lines are sorted by their final population values. The visualization uses React with D3 v5, including `d3.line`, `d3.nest`, `d3.scaleOrdinal`, and `d3.schemeCategory10` for styling. Data comes from UN population estimates CSV files, processed via a custom melt function, and rendered as animated SVG paths with transitions on the legend.