I think I've seen this puzzle before, but I really enjoyed myself gradually solving it while doing other things in the last two hours. I'm sharing this for anyone else who wants a way to spend their afternoon!
[1]: https://regexle.com
Took 4.5 min to solve #519. Would have been quicker if I started with a better strategy but it was my first time.
I thought the bigger one was more fun though, I'll continue with that one now.
#520 seems much harder tho!
What a great game, just wish the colours were configurable (colour blind)!
Really well done, but now I don't ever want to do one of these again.
With so many wildcards (`.*`) involved, it feels as though making a few assumptions along the way is unavoidable. If I start over and only make moves I can prove are correct, I don't get very far.
Edit: Solved! :)
:)
On the left a horizontal must start with F: F.[AO].[AO].*
However, the diagonal for that cell may not include an F (aside from the start): [^X]*(DN|TE|NI)
Because it's so trivially unsolvable, I had a quick look at the posted solution.
We're reading it wrong.
Take the first regex on the top row, one you included in your example:
[^X]*(DN|TE|NI)
You're supposed to fill that in from the bottom to the top.
In other words, the first letter goes immediately to the right of [^c]*[^R]*III.* - that square has to be a 'not X'. The hex immediately below it has to be an E, I, or N.