This interactive line chart visualizes population estimates for global regions from 1950 to 2100, combining data from two UN CSV files. A vertical black line marks the currently selected year, which updates when the user hovers over the plot area, prompting a re-render through a state-setting callback. The visualization uses D3.js v5 to scale time and linear axes, render multi-line paths with a basis curve, and display a categorical color legend. The SVG output includes axis tick marks, labels, and a title, all styled via CSS.