This bubble chart visualizes the relationship between city population, GDP, and land area. Each circle’s position is mapped to GDP on the x-axis and population on the y-axis, while its radius encodes area via `d3.scaleSqrt`. Tooltips, styled through CSS with a lightsteelblue background, appear on mouseover using `d3.select` and `transition` to display city-specific data. The chart is rendered in SVG with axes generated by `d3.axisBottom` and `d3.axisLeft`, and colors are assigned using `d3.scaleOrdinal` with `d3.schemeCategory10`. The data is loaded from a CSV file using `d3.csv`.