Depth of Field Effect?

Hi all,
Just trying to create a modal that zooms and blurs the background back. Based on avgrund by hakim http://bit.ly/2WG2QQR
Now it has nesting modals also with the help of @deathshadow over at codingforums.
Here is the current state:
http://bit.ly/2WGpDfw
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...

Depth of Field Effect?

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