How to animate triangular menu

Hey, I’m trying to do my final project (HTML & CSS section) in the full-stack developer course.
I figured the menu should expand from the corner of the page - experience of viewing documents.
Do you know how to animate the movement of the next section with CSS & JavaScript (I know the basics of JS & I will read what is required)?
The next section of the webpage should open on click or with scrolling.
I am interested in animation methodology, I will do the styling myself.

Neat idea! There are a couple ways of doing it, either with CSS or with JS or both, maybe depending on how you want the functionality to work. If you want it to change page with scrolling I believe JS will be required. If you want it to operate when there’s a click in a specific location then you would want to add an event listener to that location, with a callback function to perform the animation (change CSS position property). I personally haven’t played much with scrolling and JS so I am not much help there in terms of activating the animation.