Factory Loop
(Published on 13. July 2026, 11:20 by marty_sears)
Rules:
Normal sudoku rules apply.
Draw a loop, one-cell wide, that moves orthogonally between cells.
Two loop cells may only touch orthogonally if they are directly connected along the loop. Two loop cells may only touch diagonally where they are either side of a corner cell along the loop (ie; the loop doesn't 'touch itself'.)
A green circle is on the loop, and its digit indicates the number of cells in its 3x3 box that are on the loop.
A red square is NOT on the loop, and its digit indicates the number of cells in its 3x3 box that are NOT on the loop.
For any two neighbouring cells along the loop, dividing one by the other gives an exact integer (one is a multiple of the other.)
Solution code: Column 9 cells that are NOT on the loop, reading downwards
Comments
yesterday, 06:33 by MusicGusto
Absolutely brilliant
yesterday, 02:18 by Exigus
Incredible how little is needed for a unique solution. Thanks!
on 14. July 2026, 18:25 by tcmsurfer
Finally, a new Marty puzzle I get to actually solve. Thank you so much for that one, loved it.
As a novice with CTC's Simon knowledge, I was able to manage this puzzle, even though I got myself in trouble twice. Once because I didn't read the rules correctly (it's not the 3x3 surrounding cells that are counting, but the box it is in!) and once because I made a Sudoku error and a digit on the loop was wrong. Funny enough it solved the same in shape in the error state.
Thanks again1
on 14. July 2026, 13:38 by SennyK
Hats off for creating such a good puzzle with only 5 clued cells! :-)
on 14. July 2026, 11:42 by Miatc
Beautiful puzzle, such a simple setup
on 13. July 2026, 20:47 by blackjackfitz
Huzzah!
on 13. July 2026, 19:50 by Franjo
Thank you very much for creating and sharing another beautiful puzzle. You used these multiple/factor lines for your last DFM-puzzle already, so maybe it’s time to give them an official name? I’m sure that other setters will use them….
Marty: I've been calling them Multiple Lines. I've seen other people call them Factor lines though, which is fair enough... I am enjoying them at the moment!
on 13. July 2026, 19:13 by brskri
Neat puzzle, as expected from Marty. It's surprising how many restrictions can come from so little clues -- but the outcome of that is a tight solve path -- very nice.
on 13. July 2026, 19:01 by Piatato
Smooth and fun, thanks!
on 13. July 2026, 16:10 by highonlife
Ok, I struggled with this one more than I should have.
Nice Puzzle.
on 13. July 2026, 14:38 by sujoyku
Thank you for yet another wonderful puzzle, Marty!
on 13. July 2026, 14:38 by mscha
A new Marty Sears puzzle! It's been a while... :-)
Very nice one. I found the break-in fairly easy - it helps that we've had a few divisibility puzzles recently - after that it was a bit trickier, but I never got stuck.
on 13. July 2026, 13:45 by Sotehr
A true gem among Marty Sears puzzles!
on 13. July 2026, 13:36 by amirs
It took me some time in the beginning to convince myself it's not immediately broken and find the initial break in. After that it was very smooth and fun!
on 13. July 2026, 13:24 by vukkarak
I have struggled with the beginning but then it was a nice flow!
on 13. July 2026, 12:21 by pmays123
Magical puzzle! Thank you
on 13. July 2026, 12:08 by Christounet
Miraculous!
This must have taken a while to find the perfect location for the last clues.
on 13. July 2026, 11:58 by Prof.Dori
One of my favorite puzzles from Marty, just brilliant from start to finish.
