I think the reason why there is so much confusion surrounding this rule is that there is no way to cross the fence at all without meeting the definition of trapping and yet, the Q&As say that sometimes crossing the fence constitutes trapping and sometimes it doesn’t, leaving us trying to figure out where the line is drawn.
In this thread you clarified
If any part of a robot crosses the fence at all for any amount of time, it necessarily takes up some space on the other side of the fence, thereby boxing its opponent “off into a confined space” - the remaining space on the other side of the fence. Since “there is specifically no distance requirement,” this meets the definition of trapping.
However, there have been a number of Q&As in which you have ruled that crossing the fence is not trapping. They’ve been linked and referenced and re-linked a bunch of times, so I think we all can recall that they exist. I’m not going to list them here, because I’m hoping to clear up what trapping actually is, not address the unique situations of past Q&As on a case-by-case basis.
So what is trapping actually for real?
At what point does crossing the fence become illegally trapping your opponent?