beginners questions serie: if HTML is in the lightbox, how to define width in %

Hello Cedric,
I want to load HTML (any article from my Joomla website) into the lightbox. This works very well and I can define the dimensions for this lightbox also. But the width which is looking good on a desktop is too wide for a smartphone or tablet. On the latter, it will take up the full screen width. The visitor does not have the impression, to see a lightbox.
How can I achieve, that the width is defined by width: 80% height: 80% instead of defining the dimensions of the lightbox in fixed pixel values?

Hi
please don't post too much requests
you already have some requests with Mediabox CK that are not yet solved. I can not give you many answers in the same time because I need to fix them one after the other
CEd

Oh yes! – I have played around with Mediabox-CK for several days and then I have collected my questions. – Putting all these questions here at once, that is too much and it could lead to the idea, I would be very impatient.

I am sorry about that. This is the link to an experimental website, where I have created a page, to experiment with the three use cases, I want to realize with Mediabox-CK. Experimental Page with Mediabox-CK

it could lead to the idea, I would be very impatient.

yes I have understood that point

the lightbox is responsive, so please tell me how you set the width, in the plugin options ?

PS : also tested your test page, the lightbox is repsonsive

I have checked it also: In Chromium and in Firefox it shows up OK, when on desktop. But it does not, when I am using my Android with Firefox. I will check other browsers on Android next days.
You write, that you have checked my test webpage and everything seemed to be OK and responsive. May be you have checked wit a desktop browser and perhaps simulated mobile by a browser plug in. – My everyday Android 11 with an up to date Firefox shows, that your advice concerning the centering of the mediabox does not work. Independent from the kind of mediabox (video, audio, iframe with HTML) the mediabox is pushed up vertically, so that it is unusable.

Further I want to point out my original request:
But the width which is looking good on a desktop is too wide for a smartphone or tablet. On the latter, it will take up the full screen width. The visitor does not have the impression, to see a lightbox.
How can I achieve, that the width is defined by width: 80% height: 80% instead of defining the dimensions of the lightbox in fixed pixel values?

There is a need for a space to all sides around the mediabox / lightbox, when on mobile, because otherwise the user cannot realize, that he is not reading a normal article but he reads it in a lightbox. Therefore he can go on navigating on the website only, after he has clicked outside the mediabox or on the close button.