What I used to do for missing rules was reading all questions both ways. How would it work if the line was moving, then read how it would work if it isn't.
Then take that aspect out of the reading and only provide the other factors, while observing how the situation will develop.
It worked great for many rules. Not for this one, however. In this case it was clear there was something to it, yet it was also clear it wasn't working in any way provided in the open exactly.
As I said I can't go too much into rules I'm using now. If you have doubts use what AK uses, however not knowing "why" he uses it is a potential problem moving forward.
Would advice to avoid making your own rules at this point. There is time for that, but if you start doing it too early it will mess up everything potentially. With the nice example of the painter, would be like a painter using only the colors he has, and getting more colors with time. If he has 2 colors it will be challenging to be a great painting at the end yet if enough time is provided more will be added that he will know / have as a way to paint in and with enough the rules won't be to compensate missing framework and knowledge, but to build on what is already understood.
So summarize: If you don't know how a rule works would advice to not make rules at this point. It may mess up everything in the long run, making rules is for when you are very comfortable how each aspect of the system works. And of course there is always more to know, but compensating missing part with rules is not a good path.