This is based on the recent Battlefield Sudoku puzzles introduced by Big Tiger in Battlefield Sudoku #1 and Battlefield Sudoku #2. In this one the clues are all rather small; hence the name "Border skirmish".
As in Realshaggy's Battlefield Sudoku, I don't use any colored cells. (The description below is mostly copied from that puzzle.)
Fill the grid with numbers from 1 to 9, so that every row, column, and 3x3 box contains each of the 9 numbers exactly once. Consider the first X cells and the last Y cells of a row or column where X is the number in the first cell and Y is the number in the last cell. A clue outside the grid gives the sum of the digits where these groups overlap, or the sum of the digits in the gap between the groups if they don't overlap.
The puzzle is available on Penpa.
Solution code: Row 7 and row 8.
on 11. October 2020, 11:15 by Nylimb
Added penpa link.
on 6. July 2020, 13:10 by Nylimb
Added tags created by DiMono.
on 13. June 2020, 05:21 by Nylimb
Fixed broken URL.
on 13. June 2020, 05:16 by Nylimb
@Big Tiger: Thanks. I hope they do one of yours soon.
on 13. June 2020, 03:36 by Big Tiger
Congrats on getting on Cracking the Cryptic!
on 13. June 2020, 00:35 by Madmahogany
This was absolutely incredible! It took me a couple of days of staring at the grid for something to pop up. What a satisfying solve!
on 11. June 2020, 07:39 by Richard
@Big Tiger: this is exactly what I like about this platform; raising puzzle writing to a scientific level by thinking about and exploring the intrinsic logic of a puzzle type or variant. There are many more examples around here. (When I got the chance, I tend to do the same when I am writing.) That's also the reason why many of the puzzles here are not suitable for a magazine, since they require insights that goes beyond the skills of average players.
on 11. June 2020, 07:20 by Big Tiger
Clearly I have a lot to learn because I never - ever - would have thought of doing that math to get the first digit located. Wow. Can't tell if I hate you or like you, ha ha.
on 10. June 2020, 17:35 by rimodech
excellent!!!!
on 9. June 2020, 21:05 by Statistica
Ganz Klasse. Tolle Idee!
on 9. June 2020, 06:08 by Nylimb
@Richard: Thanks for the high praise!
I sort of stumbled into this. I had planned to post two more "XY-sandwich sudoku" puzzles, one of which used small clues. But when I saw some battlefield sudoku puzzles posted around the same time, I decided that posting my puzzles might confuse people, since the rules are just slightly different. Then I wondered if I could make a battlefield puzzle with small clues. Initially I tried using a logical path similar to the one in the XY-sandwich puzzle, but I couldn't make it work. Luckily I eventually thought of the logic used in this one.
I'll probably post the other XY-sandwich puzzles some other time.
on 9. June 2020, 05:59 by Nylimb
@Big Tiger: If you'd like a hint on how to start, post a hidden comment here, and I'll edit it to give a hint. That way you'll be able to see it, but other people who haven't solved the puzzle won't.
And thanks for inventing this type of puzzle!
(The offer of a hint is open to everyone else too.)
on 8. June 2020, 19:57 by Richard
Wow wow wow!
Recently I have solved quite a lot of sudokus and I rated a lot of them with five stars for beauty. For this gem it's a pity that five stars is the maximum, since I really think this is worth at least six stars!
Well, here is the sixth: *
It's clear that a lot of thinking has been done before you actually started writing. Very nice to see you exploring the intrinsic logic to the maximum!
Well done! Thanks a lot.
on 8. June 2020, 19:50 by Big Tiger
I am utterly clueless as to how to even lock down the first digit.
on 8. June 2020, 00:34 by Nylimb
@Rollo and @SirWoezel: Thanks. I've added the tag to my 10-in-9 variants.
on 8. June 2020, 00:32 by SirWoezel
@Nylimb I think it's a good idea to add every tag that describes your puzzle. For one thing, it appears that puzzles without the sudoku-tag do not show up in the sudoku-list, which I expect many visiters of this site use. And apart from that it's very well possible that the search-funcion on the site (which I have not used myself yet) also uses the tags in some way or another. In that case, not adding tags will make it a lot harder to find your puzzle.
Anyway, I'm glad I did find this puzzle as I think it's very good!
on 7. June 2020, 23:44 by Rollo
Thank you for adding the tag.
'almost every puzzle published here is a sudoku'??? 1302 of 4237! A lot of solvers here are very interested in other puzzles than sudoku and to find these it is helpful to exclude sudokus.
By the way this is no criticism, I had a lot of fun with a lot of sudokus here.
To 3D2: I would add it, because it is more a Sudoku than another type.
on 7. June 2020, 23:14 by Nylimb
@SirWoezel: I've added the sudoku tag to all of my puzzles that use standard sudoku rules. Do you think I should also add it to my 10-in-9 variants, like https://logic-masters.de/Raetselportal/Raetsel/zeigen.php?id=0003D2 ?
on 7. June 2020, 23:06 by Nylimb
Added sudoku tag.
on 7. June 2020, 23:05 by Nylimb
@SirWoezel: Actually I'd never noticed that there was a sudoku tag that I could add. I'll add it now, and will add it to some of my other puzzles too.
Thanks for the suggestion.
on 7. June 2020, 22:54 by SirWoezel
@Puzzle_Maestro Good question, but then what is the point in having a separate sudoku section if almost every puzzle published here is a sudoku?
When I visit this site, one of the first links I see is 'sudoku', which I enjoy, so I click it. I am not very interested in Slither link, ABC, Pentonimo or mystery-puzzles, which are the other 'puzzle types' in the list.
on 7. June 2020, 22:03 by Puzzle_Maestro
@SirWoezel: what is the point of only checking the sudoku-section, if almost every puzzle published here is a sudoku?
on 7. June 2020, 21:29 by SirWoezel
I only stumbled upon this puzzle by accident by the way. I usually only check the sudoku-section. Could it be you simply forgot to add that tag?
on 7. June 2020, 20:58 by dm_litv
The path to the solution is not hard. But it’s hard to find this way ;)
on 7. June 2020, 17:18 by SirWoezel
Beautiful!
on 7. June 2020, 15:28 by Mody
ein Meisterwerk
on 7. June 2020, 03:41 by Nylimb
Added link to Battlefield Sudoku #2.