YYX-Sums
(Published on 26. May 2025, 06:23 by oskode)
Rules:
- Sudoku: Fill every cell with a digit from 1-9 such that no digit repeats in any row, column or 3x3 box.
- Yin-Yang: Shade some cells such that all shaded cells are orthogonally connected and all unshaded cells are orthogonally connected. No 2x2 area is entirely shaded or entirely unshaded.
- Modified X-Sums: A number outside the grid indicate the sum of the first X runs of alternating shading in that row/column from the direction of the clue, where X is the first digit seen from the direction of the clue.
Click here to play online!
Rule Clarification:
The modified X-sums rule is satisfied for each column displayed.
The 1 sees one run of shading with the sum:
(1+2+3+4)=10
The 2 sees two runs of shading with the sum:
(2+1)+(3+4)=10
The 3 sees three runs of shading with the sum:
(3)+(1+2)+(4)=10
The 4 sees four runs of shading with the sum:
(4)+(1)+(2)+(3)=10
Ratings and comments are very much appreciated. Thank you for playing!
Solution code: The digits in column 3 from top to bottom, with a "-" between digits of different shading
Comments
on 12. February 2026, 02:12 by digim
The puzzle is really fun! It’s the first time I solved a YY-type puzzle, so I discovered a lot of insights. The X-sum variant tripped me up a lot, my mind frequently defaulted to the regular X-sum.
Took me over an hour, but I feel great solving it! Thanks for the puzzle!
on 4. September 2025, 09:38 by billychop
I've never done one of these: I've started OK, but I immediately run into a problem understanding the rules: when you say that all shaded cells are orthogonally connected, do you mean ALL with EVERY other, such that you could run a continuous path touching every single shaded cell and no unshaded cells? And the same for the unshaded ones? Thanks!
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Pretty much! You can get from any shaded cell to any other shaded cell via an orthogonal path (moving only up/down and left/right), passing through only shaded cells. The same is true for unshaded cells. Let me know if you have further questions!
on 20. August 2025, 14:50 by jubengo
Wonderful puzzle :) Loved it
on 17. July 2025, 17:59 by yttrio
Incredibly fun puzzle with a cool twist on X-sums!
on 9. July 2025, 20:52 by rainbowroad
A further rule clarification question: when a number is outside the grid, must the first run it faces be shaded?
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The first run it faces can be either shaded or unshaded, no restrictions there!
on 13. June 2025, 19:26 by Jensa
I actually got the break in pretty fast but after that it still took me nearly an hour to complete it.
Simply wonderful!
on 2. June 2025, 21:13 by Possum
Took me so long to find the break in but once it clicked, it clicked hard. Very satisfying. Thank you!
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Thanks for the kind words and for solving!
on 31. May 2025, 15:32 by Uhu
@Suxamethonium: you made a colouring mistake in row 6.
on 29. May 2025, 04:34 by Agent
Great idea and execution, very smooth!
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Thank you very much Agent!
on 28. May 2025, 10:24 by Snue
Amazing puzzle - I loved every bit of it :)
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Thank you so much, I'm glad you enjoyed your solve!
on 27. May 2025, 18:33 by madhupt
This is a fantastic, fantastic puzzle! The clues and the constraints interact so wonderfully and everything falls into place so beautifully. One of the best puzzle I have ever done. Thanks for sharing this!
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Hearing this from someone with over 1800 solves is extremely heart warming, thank you so much @madhupt!
on 27. May 2025, 16:13 by Christounet
That YY/X-sum logic is super cool and well executed. Thanks :)
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Thank you Christounet, I'm glad you enjoyed!
on 27. May 2025, 15:00 by Franjo
Absolutely amazing! Solving this puzzle made my day. Thank you so much for creating and sharing this masterpiece.
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Thank you so much Franjo for the kind words, it means a lot to me!
on 26. May 2025, 21:02 by wuc
Clever puzzle with a refreshing rule for me. Great fun thx. 3.5* to me.
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Thank you very much @wuc!
on 26. May 2025, 17:51 by Exigus
Lovely puzzle even if I thought I was going mad for 15 min but it turned out I was trying to add to 13 when it was supposed to be 14.
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Been there, done that... Glad to hear you got there!
on 26. May 2025, 17:16 by cyddrdrd
Beautiful!
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Thank you!
on 26. May 2025, 09:35 by thrutch
That felt like assembling the parts of a beautiful machine, with a big rush at the end when all the parts suddenly started working together.
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What a lovely way of putting it, thanks for the kind words!
