This bubble chart compares global cities by per-capita GDP, average temperature, and population, with bubble size encoding population and color encoding continent. It uses D3 v6 to render an SVG visualization, employing `d3.scaleLinear` for the x/y axes, `d3.scaleSqrt` for bubble radius, and `d3.scaleOrdinal` with a category color scheme. Data is loaded via `d3.csv` from a GitHub Gist, and the chart includes both color and size legends.