Coder2Mo/Calendar ? reverse-engineered prompt

Build me a simple calendar web app that looks clean and works in the browser with just HTML, CSS, and JavaScript.

I want a monthly calendar view with the days laid out in a neat grid, plus buttons to move to the previous and next month using arrow icons. It should show the current month and year clearly, and highlight today when it’s visible. Keep the design minimal and responsive, with a friendly polished look that matches a small personal project.

Use the existing page structure and make sure the calendar updates correctly when I click through months. If you need to check anything, look up current browser friendly ways to do it. Keep everything straightforward and easy to understand, since this is meant to be a simple calendar app people can open and use right away.