Focus onto control that only appears on focus?

Hi all,

I have a question about focusing onto a control that is opacity: 0 when not
focused.

So you hit "Tab" and you are taken to a control that has opacity: 1 set on
its :focus pseudo selector, thus it was invisible and it only appears on
focus.

When focused, the control will have a focus ring.

I know this isn't ideal UX, but is this disallowed under any criteria
please?

Thank you