This example is a hands-on coding exercise built with D3.js v4 that teaches SVG manipulation and animated transitions. The page displays a static SVG canvas containing a blue rectangle, a red circle, and a yellow square, alongside a button that triggers a JavaScript function to run D3 code. The function programmatically appends a new green rectangle, animates its position using `transition().duration()`, and begins mapping an array of color data to new rectangle elements via `append()` and `attr()`. The code demonstrates core D3 concepts like selecting, appending, and transitioning SVG shapes, with an accompanying exercise checklist for learners to complete.