Circles on a Map
This visualization displays the population of countries as circles on a natural Earth projection map, with the area of each circle proportional to the country's 2018 population. It uses d3.geoPath for geographic boundaries and d3.scaleSqrt for sizing circles, while enabling pan and zoom through a zoom event handler. Hovering reveals tooltips with population details via title elements. The visualization sources data from a CSV file merged with TopoJSON geometries, rendering through d3 and SVG, and includes a custom size legend with tick marks for population values.