This bubble chart plots U.S. cities by population density on the x-axis and land area on the y-axis. Each bubble’s size encodes the product of these two variables, representing total population, with a legend showing bubble-size equivalents for specific density values. Built with D3.js v7, it uses `d3.scaleLinear` for both axes, `d3.scaleSqrt` for bubble radius, and `d3.axisBottom` and `d3.axisLeft` to render tick marks. The visualization displays city names via hover effects, with a static CSV data source.