Depth of Field Effect?

Hi all,

Just trying to create a modal that zooms and blurs the background back. Based on avgrund by hakim https://lab.hakim.se/avgrund/

Now it has nesting modals also with the help of  @deathshadow over at codingforums.

Here is the current state:
https://jsfiddle.net/postcolonialboy/1jz0q3xk/19/

Now, what I am trying to do is:
by clicking the nested modal link, everything should be pushed back again and blurred - like simulating receding layers/depth of field.

I've attached an image to explain this: https://ibb.co/LNB83jm

Thanks