This took over half a year between coming up with the core idea and finally making a revision I was satisfied with. Thanks to Qodec for helping workshop an earlier draft, and several others for testing the several dozen other revisions along the way.
Fun fact, some of the drafts I went through became entirely separate puzzles, which I may post here at some point.
RULESSolution code: Rows 1 and 9 of the grid, in that order, left to right with no spaces (e.g. 123456789987654321)
on 4. August 2022, 20:27 by Playmaker6174
Very interesting solve with some cool ideas in it :)
on 15. June 2022, 16:57 by Gullie
Wow, what a great puzzle this was. The first time I tried it I got really stuck and even bifurcation didn’t get me anywhere. Tried again today and finally discovered the break in logic. Excellent puzzle!