Rainbow Constraint
(Published on 17. June 2025, 00:02 by ebiggie)
RULE SET:
Normal Sudoku rules apply. Place the digits 1 through 9 in each row, column, and box.
KROPKI: Cells separated by a black dot are a 1:2 ratio. ALL dots are given! There is a negative constraint for black dots in this puzzle.
KILLER CAGES: The sum of the cells in a cage must equal the total given for that cage. Digits in a cage do not repeat.
DUTCH WHISPER (ORANGE): Adjacent digits along the orange Dutch Whispers line must differ by at least 4. Digits may repeat if other rules allow.
PALINDROME (GREY): Digits along the grey palindrome line must read the same forwards and backwards.
GERMAN WHISPER (GREEN): Adjacent digits along the green German Whispers line must differ by at least 5. Digits may repeat if other rules allow.
REGION SUM LINE (BLUE): Box borders divide the blue line into segments of the same sum of values.
RENBAN (PURPLE): Digits along the purple Renban line must be a set of consecutive non-repeating digits, and may appear in any order.
For our color blind friends:
There's only one of each line type in the puzzle.
From left to right: Dutch Whisper, Palindrome, German Whisper, RSL, Renban.
Click the Link to Play: Sudokupad
Solution code: Please provide the digits from row 9 (left to right):
Comments
on 26. July 2025, 10:08 by frosto
ahhhh, the negative constraint...
Once you remember it it flows like a charm.
Very nice puzzle.
on 23. June 2025, 11:36 by TommiH
Lovely puzzle! That negative constraint cannot be emphasised any better (unless Sven implements a flashing text that hovers on top of the puzzle all the time) and even though I totally knew it was ther I was at times trying to solve the puzzle without using it, making it harder for myself. Silly brain. Anyway, great puzzle!
on 19. June 2025, 22:19 by ebiggie
Wow! I can't believe so many missed the negative constraint rule. I will heavily highlight that in the rule set for future puzzles! Thank you everyone for all the comments :)
on 19. June 2025, 15:34 by JVA
darn negative constraint
on 19. June 2025, 00:33 by maiaz
If you get stuck just before the end, you've forgotten the negative constraint. It's almost (but not quite) possible to solve without it.
Probably worth putting in something to highlight the negative constraint given how many comments are about misssing it.
on 19. June 2025, 00:32 by maiaz
If you get stuck just before the end, you've forgotten the negative constraint. It's almost (but not quite) possible to solve without it.
on 18. June 2025, 13:32 by TeddieMilo
Missed the negative constraint. Very nice.
on 18. June 2025, 05:49 by gregui
Very cool looking! And also nicely done. I spent way longer than I should have for not reading the rules entirely :/
on 18. June 2025, 03:48 by shikage5
Reading comprehension will be the death of me -_-. Great puzzle once I knew what I was doing
on 18. June 2025, 00:22 by garycblack
just the last 4 cells before the negative constraint was required. I knew I missed something when I saw the deadly pattern!
on 17. June 2025, 20:51 by josemadre
Negative constraint...reading is fundamental, I feel silly
on 17. June 2025, 19:39 by Myfyr MJ
Very nice and easy puzzle
on 17. June 2025, 16:05 by PinkNickels
I made this one so much harder by not reading the rules carefully. LOL
on 17. June 2025, 01:22 by bbutrosghali
This was much easier once I fully read the rules
on 17. June 2025, 01:14 by sujoyku
Same here. Re-reading rules made it much less impossible. :)
Thank you for the fun puzzle, ebiggie!
on 17. June 2025, 01:13 by BrendanD
Oops..missed that! Sorry
on 17. June 2025, 01:04 by GorgeousNicko
@BrendanD
No, there isn't - but you may need to read the rules again. I certainly did!
