This visualization displays a row of colored circles, each representing one of the 20 swatches in d3’s category20 color scale. The example renders circles as SVG elements using D3’s data join pattern, binding an array of 20 values via `d3.range`. It positions each circle along a horizontal linear scale for the x-coordinate and applies the category20 scale directly as the fill color. The page loads D3 v3 from a CDN, and the visualization uses the `d3.select` and `append` APIs.