Can't Spell Index Without X (with ChinStrap)
(Published on 10. March 2025, 18:16 by sujoyku)
- Normal sudoku rules apply, i.e. each row, column and 3x3 region has to contain the digits from 1 to 9 once each.
- Index Lines: Each turquoise line is an Index Line, i.e. the digit in the Nth cell along such a line (starting from the diamond) indicates the position along the line where the digit N appears. For example, if a diamond cell contains a 3, the third cell along that line must have a 1.
- X-sums: Clues outside of the grid are X-sum clues, i.e. the numbers indicate the sum of the first X digits in the respective row or column where X is the first digit seen from the clue. An odd/even clue only indicates the parity of the respective X-sum.
Here you can solve the puzzle online:
Solution code: Row 8 from left to right (9 digits in total)
Comments
on 23. April 2025, 00:36 by Lenivaya_Joppa
Thank you for this very nice puzzle, dear sujoyku and ChinStrap! :)
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You are much welcome, Lenivaya_Joppa, thank you for your comment! We are glad you enjoyed the puzzle.
Kind regards, sujoyku
on 14. March 2025, 19:55 by dzamie
You guys are getting me to start really liking Index Lines! I found this to be more of a 3*, though that might have to do more with my inexperience with both rules. Still, after a fair bit of puzzling stuff out, it all solved really well. I enjoyed that both the X-sums and Index Lines stayed relevant until just about the end, rather than being quickly marked off and turning into a standard sudoku afterwards.
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Thank you for your comment, dzamie! We love to hear you are warming up to the Index Lines. (Probably not a huge surprise, they are a favourite constraint of ours.) Regarding difficulty, we initially uploaded it as 3 stars, but it might be somewhere around 2.5. In any case, we are glad you enjoyed the puzzle.
Kind regards, sujoyku
on 11. March 2025, 17:42 by Franjo
Sehr schöne Kombination! Dieses fabelhafte Puzzle zu lösen hat großen Spaß gemacht. Vielen Dank dafür.
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Sehr gern geschehen, Franjo, vielen Dank für deinen freundlichen Kommentar! Wir freuen uns, dass Dir die Kombination aus X-sums und Index-Linien gut gefallen hat.
Herzliche Grüße, sujoyku
on 11. March 2025, 14:57 by Visumation
Very nice. Really nice flow. I second @Snookerfan on difficulty. 12 min. for me. But definitely rated it very nice. Thanks a lot guys. Great fun.
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You are much welcome, Visumation, thank you for your comment! We are glad you had a fun solve.
Kind regards, sujoyku
on 11. March 2025, 10:36 by Snookerfan
Very nice and smooth as usual! I rated it as easy because of the relatively quick solve time, although one x-sum clue was probably a bit harder to use. Thank you
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You are much welcome, Snookerfan, thank you for comenting! We are glad that you liked the puzzle. Concerning difficulty, one could maybe argue if it should be 2 stars, 3 stars or somewhere inbetween those. Thanks for sharing your take.
Kind regards, sujoyku
on 11. March 2025, 09:02 by TheNineElements
Solve Time 66:28
I rated this 3/5 difficulty.
Really nice puzzle! It was trickier than I expected, but was overall enjoyable and interesting to work through.
My solve time was definitely on the longer end for 3* puzzles, and the puzzle logic felt like a harder 3* puzzle. I think I could have solved this puzzle a bit quicker if I didn't take a break mid-solve, but it would've taken me around 60 minutes regardless, which matches up with hard 3* puzzles for me.
The break-in was really interesting and I definitely liked how the logic bounced from one clue to the next. In the early phase, I felt like I "worked backwards" to make deductions that led to decent progress, and the interactions between the seemingly unrelated rules/clues made for a memorable solve. The break-in felt somewhere around 2-3* difficulty.
I got pretty stuck in the early midgame (after placing a few digits/pencilmarks), and I ended up spending nearly 40 minutes on the 8-length index line, making only small deductions and not placing any digits. I wasn't totally idle during that time, but all the deductions/eliminations I made were very minor and it took a long time to whittle down some cells until I finally placed more digits. The deductions were actually quite complicated (tracing logic across several different clues around the grid, figuring out how multiple x-sums interacted with each other and with the index line), and felt like a high 3*-low 4* level of difficulty. I'm not sure if I should have started elsewhere to have a more straightforward solve path, but in the end I was able to work out several digits on that line. I suspect there is a simpler "trick" or deduction (that I missed), which would have made me progress much quicker through the solve - but I didn't really make an effort to look for it because I was making consistent progress (albeit slowly). I didn't even look at the 20 x-sum clue during that time, but looking back, I feel like I totally ignored logic that arose from that area of the puzzle until I had already spent a long time on the other line & x-sums.
Once I made some big progress on that line, the remaining lines & puzzle logic was much more approachable and felt around 2* difficulty. Even though several parts of the puzzle were approachable/straightforward, the difficulty in the early midgame definitely tilted my overall rating to 3*.
Overall, this was a great puzzle! Definitely worth solving if you have the time to work through it!
**
Thnk you for your detailed feedback, TheNineElements! We are glad that you enjoyed the solve.
Kind regards, sujoyku
on 11. March 2025, 01:25 by aqjhs
you really can't spell index line without "×Chinstrap" :D
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And if you could, you shouldn't. :)
Thank you for your comment, aqjhs!
Kind regards, sujoyku
on 10. March 2025, 23:24 by lootyloot
I love these index lines puzzles. This puzzle was so smooth and enjoyable that it felt like a 1-star sometimes. Thank you
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You are much welcome, lootyloot, thank you for commenting! We are glad you had an enjoyable solve.
Kind regards, sujoyku
on 10. March 2025, 21:14 by sfield
I really liked how the simple rule set lead to a varied dynamic. Well done.
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Thank you for your comment, sfield! We are glad you liked the dynamics introduced by these constraints.
Kind regards, sujoyku
on 10. March 2025, 20:38 by wuc
Very smooth clever puzzle thx.
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You are much welcome, wuc, thank you for comment! We are glad you enjoyed it.
Kind regards, sujoyku
on 10. March 2025, 19:52 by cg24
perfekt wie immer :) ihr seid wirklich ein ganz tolles Team und eure Rätsel machen durchweg einfach nur Spaß
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Danke für deinen Kommentar, cg24! Wir freuen uns, dass Dir unsere Rätsel Spaß machen.
Herzliche Grüße, sujoyku
on 10. March 2025, 19:07 by ChinStrap
Lovely working with you as always :)
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Thank you, ChinStrap! Setting a puzzle with you always means happy setting. I hope we get to collab many more times in the future.
on 10. March 2025, 18:54 by Elliott810
Brilliant puzzle with a very smooth solutuion path! Thank you:)
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You are much welcome, Elliott810! We are glad you had a smooth solve.
Kind regards, sujoyku
