This interactive line chart visualizes population change over time for global regions, allowing users to select a specific year by moving the mouse across the plot. The visualization highlights the selected year with a vertical line, while each region’s trajectory is color-coded via an ordinal scale. The chart uses d3’s `scaleTime`, `scaleLinear`, `axisLeft`, `axisBottom`, and `line` generator with `curveBasis`, and loads UN population estimates from CSV data. The legend is built using a custom `colorLegend` component.