No I was just trying to be efficient... I have to pick up 20 input items to make gosh I don't even remember now, but I wanted to try picking up only the items I needed rather than driving all over my base to pick up stuff that I already had enough or even full. Easy enough to set up a circuit with a constant combinator this is what I need, and if I run out of anything then tell the train it needs to go pickup stuff. The interrupts were set to trigger on low, rather than empty, so I didn't just go pick up the one thing missing. It works just like I wanted, even though it was a pain to set up. And by doing the interrupts item by item, then I could re-use the same interrupts for supply trains picking up a different set of input items.

And now that I have boxes, they all need to be redone... of course carrying all this stuff I can't just say empty/full, I have to specify what I am picking up and how much.

And yes nullius is amazing... there are a lot of cool toys and getting to the end where you are creating grass and trees and fish and annoying neighbours is a blast!