This example displays a scatter plot of automotive data, showing the relationship between miles per gallon and horsepower. Each circle encodes vehicle weight through color and engine displacement through size, with interactive tooltips revealing the car model name. The visualization is built using the Vega-Lite API, which composes specifications programmatically, and renders through Vega with D3.js for data loading via `d3.csv`. The data originates from the classic auto-mpg dataset hosted as a GitHub gist.