Maybe it's just me, but no matter which way I approach this or try to solve it (and I've tried four different times now), I can't seem to figure out how to solve it. Is there something I'm missing here?
Thank you! Took me another two tries (one where I missed up an easy mistake early on and screwed me over by the end), but I got it, and I can see exactly why I went wrong. Very good and cute.
SPOILER:
R1, column 7 - 11, column 15-19.