Megaton Nine-Tails Rush (OP07-078) [500 Years in the Future]

[Main] If the number of DON!! cards on your field is equal to or less than the number on your opponent's field, set up to 1 of your [Foxy] cards as active.
<br>[Trigger] Add up to 1 DON!! card from your DON!! deck and set it as active.