Question: This is very simple example of what I want to get. My question is about @returns tag. What should I write there? 

```js
class Base{
  /**
  * @returns {QUESTION: WHAT SHOUL BE HIRE??}
  */
  static method(){
    return new this()
  }
}

class Sub extends Base{
}

let base= Base.method() // IDE should understand that base is instance of Base
let sub= Sub.method() // IDE should understand that sub is instance of Sub

```

Answer: 
I did it for you with MU Grids and media queries, if you have questions, ask. I am always ready to help. This is codesandbox link. Let me know if it help you.
<https://codesandbox.io/s/charming-shirley-oq6l5>
Thanks to both, it solved the main part o what i need.

Also need to implement a change of page.
I forget to mention that the map will be React-Leaflet,
so need to implement a flap button over the map for the mobile version.

The button is for scroll to up, because any finger movement in the map area only will affect the map content.
Do not will have effect in the scroll.

[![enter image description here](https://i.stack.imgur.com/ZNcER.png)](https://i.stack.imgur.com/ZNcER.png)

Another thing to implement is the break page concept:

The behaviour of the break page is like when you see a pdf in presentation mode and press
the keyboard button Repag - Avpag, it change all the content and never see the half top and the half down.

Grettings