This choropleth map visualizes global population density across selectable years (1980, 2000, 2010, 2022) using a Mercator projection via `d3.geoMercator` and `d3.geoPath`. A threshold color scale maps density values to a blue sequential palette, with country-level data loaded from a raw GitHub CSV. Users interact through a dropdown to switch years, triggering map redraws and an animated tooltip on hover showing country name and density. A sidebar ranks the top ten most densely populated countries for the chosen year.