This line chart visualizes global population trends by region from 1950 to 2100 using UN population data. A black vertical line marks the currently selected year, and hovering over the chart updates the selection to the nearest year, shifting the line accordingly. The visualization uses d3’s `scaleTime` and `scaleLinear` axes, a `line` generator with `curveBasis` for smoothing, and a color legend built with `scaleOrdinal` and `schemeCategory10`.