This visualization shows population change over time as a set of semitransparent, overlapping lines, with each line representing a different region and a color legend on the right. The data comes from a CSV file containing UN population estimates and projections, melted into a tidy format before rendering. Built with D3 v5, the code uses `d3.nest()` to group data by region, `d3.line()` with `curveBasis` for smooth paths, and `d3.scaleOrdinal` with `schemeCategory10` for colors. The chart is rendered as SVG with axes, gridlines, and a custom color legend component.