A dot means that the sum of the digits in the two neighbouring cells is a prime number. All dots are in the grid.
Solution code: Column 5, followed by row 9.
on 21. November 2022, 15:01 by Nick Smirnov
Penpa:
https://tinyurl.com/2zml2hac
on 29. July 2012, 08:21 by Oliver Strauß
Richard, thank you for this puzzle design. It took a huge number of starts to solve it.
on 24. April 2012, 14:54 by silesia
danke für die schnelle Hilfe! Jetzt kanns losgehen!
on 24. April 2012, 14:30 by Richard
@silesia: rechts unten ist drei mal P
on 25. February 2012, 11:26 by Mody
Ganz großartige Konstruktion
on 24. February 2012, 14:05 by Alex
nice tricky one ;)
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