This example visualizes the relationship between alcohol content, average residual sugar, and average wine quality in red wine samples. It displays grouped averages of residual sugar as light-steel-blue bars and average quality as a dark-orange line across rounded alcohol levels, with a legend distinguishing the two metrics. The visualization uses d3.csv to load the winequality-red dataset, then applies d3.rollups to compute grouped means. Bar and line geometries are generated with SVG rect elements and the d3.line generator, while d3.scaleBand and d3.scaleLinear map the data to axes.