This example shows the S&P 500 index price over time as a filled line chart, using an area mark to emphasize the trend. The Vega-Lite specification defines a temporal x-axis for dates and a quantitative y-axis for prices, with a fixed chart width. The data is loaded from an external CSV file hosted on GitHub, and the visualization is rendered in the browser using the Vega-Embed API, which combines Vega and Vega-Lite libraries.