This example demonstrates fundamental SVG shapes and interactive CSS styling. It displays a red rectangle, a green-bordered circle, and a thick black line on an 800 by 800 canvas. The rectangle uses a CSS transition on all properties, causing its fill and stroke-width to animate over three seconds when hovered, turning green and widening its border. The code directly uses SVG elements (`rect`, `circle`, `line`) and CSS selectors, including a `rect:hover` pseudo-class and the `transition` property.