This example renders a simple HTML page that displays the text "HI I'm 정융" as a heading, followed by a JavaScript-generated alert showing a variable's value. The page uses vanilla JavaScript to write red-colored text and a concatenated message about the user's age directly into the document. Styling is applied via a linked CSS file that sets paragraph and heading colors to green with a yellow background. The code relies on core JavaScript `document.write` and `alert` functions, along with basic CSS selectors, to create a minimal interactive demonstration.