Two side-by-side D3.js v7 scatter plots show vehicle Horsepower versus Torque, with circle size encoding MPG and color encoding make (Audi, Chevrolet, Volvo). The first plot renders fully opaque, while the second applies low opacity to reveal overlapping points. Both use `d3.csv()` to load data, `d3.scaleLinear()` for axes and sizing, `d3.select()` for SVG element creation, and mouseover handlers to display tooltips with exact values. Axes, titles, and a size legend are drawn as SVG text and shapes.