Question

I’m trying to transition a child element when the parent element is focused.

I want to do something like:

parent:focus{
//do something to first-child
} 

Is this possible, or does this require JS?

Answer 1

I’m not sure if this is what you mean, or not. If you do…

.parent:active .child {
    /* Style */
}

The style will be applied to .child elements inside the focused .parent.

Here’s a fiddle that shows how it works. You can click anywhere in the big div to change the smaller (child) divs.