Five blue squares animate their width and height from zero to the values in the rectData array (100, 200, 300, 400, 500), growing at a 0.3 opacity on a 960-by-500 SVG canvas. Using D3 v5 and the select API, the visualization attaches a transition to the enter selection of each rectangle, applying a 5-second duration with a 250-millisecond delay to both dimension changes simultaneously.