This example demonstrates how to combine SVG shapes with CSS styling to create a simple interactive visualization. It shows a red-background SVG canvas with geometric elements styled through custom CSS classes, including highlighted shapes and line properties. The code uses D3 v7 for SVG selection and attribute manipulation, specifically the `d3.select` method to target the SVG element and apply the background color. The visualization includes CSS-defined classes for line styling, such as stroke color and width, and path-specific properties like stroke-linejoin. Built as a React application, the example renders through standard SVG markup within an HTML page.