There are a few grey lines shown in the grid. The digits on the line form a palindrome i.e. it is a sequence of numbers that read the same from start to end of line and backward e.g. 1234321 etc.
Lösungscode: The main diagonal goes from top left to bottom right, then the row 5, 18 digits.
am 25. August 2022, 01:56 Uhr von cdwg2000
Added CTC link.
am 21. September 2021, 07:25 Uhr von cdwg2000
Repaired txt.
am 17. Februar 2021, 02:54 Uhr von cdwg2000
Increase difficulty.
am 29. Januar 2021, 05:17 Uhr von cdwg2000
Add break-in method picture.
am 6. Januar 2021, 17:19 Uhr von cdwg2000
Further tips, add about Gurth's symmetrical placement theorem.
am 3. Januar 2021, 16:03 Uhr von cdwg2000
Increase difficulty.
am 2. Januar 2021, 15:29 Uhr von Fedo
Wow that was nice! It took me a while but nice solve!
am 2. Januar 2021, 14:59 Uhr von cdwg2000
Repaired hint txt.
am 1. Januar 2021, 23:26 Uhr von cdwg2000
Repaired txt title.
am 1. Januar 2021, 15:36 Uhr von cdwg2000
Added txt hint.
am 1. Januar 2021, 12:55 Uhr von cdwg2000
The hint is in the text and the solution code. If you need further hints, please let me know through the hidden comments.:-)
am 31. Dezember 2020, 21:45 Uhr von cdwg2000
Fixed F-puzzles link.Provides more detailed rules.
am 31. Dezember 2020, 21:22 Uhr von jchan18
https://f-puzzles.com/?id=y8hxhvxr