Rainbow Cells
(Published on 5. February 2026, 11:43 by balpha)
Normal Sudoku rules apply.
The orthogonal neighbors of a rainbow cell contain at least two different pairs of digits with each pair having the difference as indicated on the rainbow cell.
For example, a 3 surrounded by the digits 1, 2, 4, and 5 is a valid rainbow cell, because both 1/4 and 2/5 have a difference of 3.
The two pairs may have one digit in common, but not both (as that wouldn't make different pairs).
For the avoidance of doubt, the pairs must have different digits, not just come from different cells. For example, a 6 surrounded by a 1, a 2, and two 8s is not a valid rainbow cell, because pairing the 2 with two different 8s still gives identical 2/8 pairs.
Solution code: Row 7 (third from the bottom), left to right
Comments
on 5. February 2026, 19:17 by balpha
Clarified German rules per @superkinkel's comment.
on 5. February 2026, 19:09 by superkinkel
Es ist zwar aus dem Kontext heraus verständlich, aber "senkrecht" bedeutet nicht "orthogonally", sondern "vertical". Auf Deutsch heißt es "orthogonal" oder "rechtwinklig".
[balpha:] "Senkrecht" kann beides bedeuten ("zwei Geraden stehen senkrecht aufeinander"), aber du hast Recht, an diese Doppeldeutigkeit hab ich nicht gedacht. Ich passe das mal an. Danke!
on 5. February 2026, 18:21 by zeniko
That‘s an interesting, fresh rule, which I‘ve found to be far trickier than expected and which kept resisting quite far into the solve. Thanks for sharing.
on 5. February 2026, 16:02 by balpha
Fixed solution code description.
on 5. February 2026, 15:24 by Siebuhh
Note: the solution code is row 7 (third from the bottom), not row 6 :)
[balpha:] Ooops, thank you for pointing that out! Fixing now.
