Responsive design projects... Do I need to use Javascript?

I almost completed the Responsive web design course and now I need to build the projects that it ask in the end. But I have a question. Since this course is only about HTML and CSS, why it asks me to use Javascript, like it says on this following link?

Thank you for paying attention!

You don’t have to use JS. It just says that using it is optional if you want to spice it up (you should eventually differentiate your tribute page if you want to use it as a portfolio project).

But right now you can finish the project using only HTML/CSS.

Ok, thanks Virgil. Just one more question: do you suggest me to build the page directly on Codepen or you think it is better to write the code on a IDE and then paste it on Codepen?

The Javascript is to test the site to make sure you pass. That’s it. You need to link that and make sure it passes the tests.

You can do either way but if you build it outside of codepen and paste it in be aware that code pen takes care of things on the back end. like headers and code outside the tag…so it may not behave correctly.

Thank you very much!