How to make responsive layout inside iframe?

Question

css

Let's say that the site contains an iframe inside an advertising banner, the iframe sizes are equal to the size of the banner, respectively. With certain actions inside this iframe, a form with a checkbox is loaded.
If the banner size is, for example, 300*250, then the form is displayed correctly. If 640*63, then the shape looks crooked and is cut off at the top.
You need to layout this form so that it adapts to different sizes of the banner/iframe. With adaptive page layout using, for example, media queries, css indicates the location of elements depending on the screen width. And how to do in this case, i.e. depending on the dimensions (width) of the iframe? How to write it in css?
I will be grateful for any advice.

Answer 1

It is necessary for different sizes of banners, to load a different code. It's easier than trying to shove the unimpressible