This example generates a colorful grid of rectangles using D3.js. The visualization displays twenty rectangles arranged in a responsive layout, with each rectangle's fill color cycling through a palette of six distinct colors. The code leverages the D3.js library (v6) to select the chart container, append an SVG element, and join data to SVG rectangles using the `selectAll`, `data`, and `join` methods. The SVG renders at half the window's width and full height, with a light cream background.