Do Not Cross (Infections)
(Published on 28. October 2026, 17:31 by gdc)
Infection Sources: Each digit matching its box number is an "infection source". Each row and column contains an infection source. They are infected.
Transmission: Infected cells infect all smaller orthogonal neighbors. Infections keep spreading until no infected cell has a smaller uninfected orthogonal neighbor. (Every infected cell can be traced back to one or more infection sources).
Battenberg: A 2x2 forms a checkerboard pattern of infected and uninfected cells if and only if there is a striped cross on its central vertex.
Kropki Tablets join consecutive digits.
Example Puzzle
A 6x6 puzzle with the same rules and its solution. Colors: Orange for Infection sources, red for secondary infections and green for uninfected.
Solution code: Uninfected cells in column 5, top to bottom (up to 8 digits).
Comments
yesterday, 12:22 by flutchman
This is problematic.
I couldn't solve this, but was intrigued. And unfortunately, this lead to me bingeing the whole series. So far so good.
But now I've finished this one and I crave moooore BRAAAAAINS, erm puzzles. I definitely meant to write puzzles.
When's the next one coming :)
yesterday, 09:17 by Christounet
Sick! Thanks :)
on 29. October 2026, 14:41 by madhupt
Beautiful puzzle! Flows really nice but can be very very confusing. The last bit of logic which unravels everything is quite beautiful. Thanks for sharing this.
on 29. October 2026, 05:46 by henrypijames
Another opportunity for me to give a shout-out to Sea Level Rise (#HEV), featuring similar logic of orthogonal cascades.
on 29. October 2026, 03:16 by gdc
remove redundant kropki
on 29. October 2026, 01:06 by Calvinball
Another great entry to one of my favorite sudoku series!
on 28. October 2026, 20:59 by PrissyP
My first solve of the series and I enjoyed it a lot. I will definitely try some of the other episodes of Norma :)
on 28. October 2026, 20:14 by emoney1374
Great puzzle! Glad to see another installment in this series
on 28. October 2026, 17:46 by jakestilesowen
A super fun series continues! Play all of gdc's Infections puzzles!
