This example visualizes the Iris dataset with a scatter plot of petal length against petal width, coloring each point by species (setosa, versicolor, or virginica). It also encodes sepal length and width as additional attributes on the circle elements. The code loads CSV data via `d3.csv`, uses `d3.scaleLinear`, `d3.extent`, `d3.axisLeft`, and `d3.axisBottom` to render SVG circles and axes, and styles the page with CSS. The data comes from a remote gist URL.