A scatter plot of 120 cars from the classic fuel-economy dataset, with axes, color, and point size mapped to numeric and categorical columns via dropdown menus. The D3 v7 reusable component uses `d3.scaleLinear`, `d3.scaleSqrt`, and `d3.scaleOrdinal` with `d3.schemeTableau10`, rendering SVG circles with animated transitions. Grid lines, axes, tooltips, and legends update dynamically when the user selects different columns.