Liar X-Sums Cipher (ft. rdrd)
(Published on 18. January 2026, 23:58 by Christounet)
This is the second puzzle I set with rdrd. You can find our first collab puzzle here. It was a lot of fun working together on these puzzles and we're really happy with what we came up with. Thanks to all the testers for testing several versions and for their suggestions. Difficulty should be between 4 and 5. Do try the example puzzle that has some logic not used in the main puzzle. Other puzzles with liar X-Sums coming soon hopefully. Have fun!
The puzzle :
Rules :
- Normal sudoku rules apply
- X-Sums : Clues outside the grid represent the total of the first X digits in that direction, with X being the digit in the first seen cell.
- Liar X-Sums : For each row/column with clues, two clues are provided. Only one of them (top or bottom, left or right) is correct. The other clue is lying and can never be correct.
- Cipher : Clues are encrypted. Each distinct letter represents some unique digit from 0-9. A "?" is a stand in for any digit 0-9, but for a single digit or double digit number, the first digit may not be 0.
Example puzzle (without the cipher):
Solution code: The digits of the true X-sums, for row 6, row 8, column 6, column 7, in reading order (left to right, top to bottom). For the example puzzle, column 1, row 4, it would be 321426.
Comments
on 26. January 2026, 20:30 by hepcecob
The break-in logic was completely new to me, granted I haven't had much experience with x-sum puzzles. This was beautiful all the way through.
on 24. January 2026, 12:44 by henrypijames
Took me more than two hours and innumerable mistakes to finally (and correctly) break in.
Wording of the solution code prompt is ambiguous: "digits of the sum" can be understood as just 15 instead of 54321.
on 19. January 2026, 10:30 by Piatato
Amazing puzzle, so much fun, especially figuring out the opening phase. Thanks for the splendid work!
on 19. January 2026, 00:11 by cyddrdrd
Enjoyed a lot collaborating with you on our second puzzle. Exploring this ruleset together was a blast. Looking forward to the next one :)
