Hello HTML
This example shows a single red square rendered in SVG, which transitions to green with a thicker border when hovered. The page uses plain HTML, CSS, and JavaScript, with a 1000x1000 SVG element containing a `<rect>`. The CSS defines the shape's stroke, fill, and a 3-second transition on those properties, triggered by the `:hover` pseudo-class. No external libraries are used; it demonstrates basic SVG and CSS interactivity.