test application of patient flow
A simple D3.js animation shows a hospital with five patients as colored circles inside a rounded rectangle. Apples are red and large, lemons are yellow and small, drawn via scales from the d3 module. The code uses `scaleOrdinal` for colors and radii, then updates the visualization over time with `setTimeout`: one patient is removed, a type changes, and another is filtered out, demonstrating data joins, enter/update/exit patterns, and SVG rendering.