This example demonstrates a simple interactive color-changing interface. The page displays two text messages, “Hallo Welt!” and “HALLO!!”, centered on a light-yellow background. Clicking the “Ändere die Farbe” button toggles a `pink` CSS class on both the first message and the button itself, changing their background colors. The implementation uses vanilla JavaScript with `document.querySelector` to select elements and `addEventListener` for the click handler, while the visual styling relies on standard CSS classes and transitions.