Generally speaking, theme entries are all across clues, symmetrically placed, something like this:
However, if you’re a boss, you can make it work that the theme clues are STILL symmetrical, but some across and some down. This means that they have to cross each other symmetrically, e.g:
I wanna write a util that, given a set of theme clues, says whether they have symmetric crossings.
Moreover: often I'll have one or two themers that I'm very excited about, and then a whole bunch more that I'm equally okay with, which leaves me free to choose based on grid suitability. I would like this util to be able to take in a BUNCH of possible theme clues and spit back out the ones that can be symmetricly crossed on a grid.