RAT RUN 38: Synchronicity
(Published on 20. May 2026, 01:10 by marty_sears)
Rules:
Normal sudoku rules apply.
AIM OF EXPERIMENT: Finkz and Phinx must both reach different cupcakes by finding a path through the maze. The paths must not visit any cell more than once, cross themselves or each other, or pass through any thick maze walls. There is no space to move diagonally in this maze.
BLACKCURRANTS: If a blackcurrant sits between two digits, one is double the other.
ONE WAY DOORS: A purple arrow always points to the smaller of the two digits it sits between, and may only be passed through in the direction it's pointing.
TEST CONSTRAINT: In this experiment, any two digits visited adjacently along a path must be different parities (one is odd and the other is even), and also have a difference of at least 5.
Solution code: Digits in row 5 not visited by either rat, from left to right
Comments
on 23. May 2026, 15:08 by jennyaa
When can we buy that Finkz plushie?
on 22. May 2026, 14:45 by akodi
I'm intrigued... why Elliot is referencing experiment 39 specifically.
He must've written this weeks ago...
on 22. May 2026, 10:55 by vukkarak
One of the easiest but still brilliant
on 22. May 2026, 00:36 by YellowMug
After the ceruleans viridians burgundies here we are with yellow. And then we have vermilion next. What colours do we have left… periwinkle?
Marty your vocabulary of colours is almost as amazing as the puzzles :)
on 21. May 2026, 16:06 by blackjackfitz
Huzzah!
on 21. May 2026, 09:47 by buh
those rats do be running
on 21. May 2026, 04:05 by l_ugray
A delight as always! With Simon’s solve delayed, would you consider giving your setter’s story comment here? I always greatly enjoy reading it after my solve.
Marty: hehe glad you enjoy those! I think I'm going to be annoying and make you wait until Simon's solve until you read the story of how I set this. There's quite a lot to say about it :)
Fair enough! I’ll look forward to it.
on 21. May 2026, 02:38 by compiling
Haha, wow. My first impression was that it should be absolutely impossible for 4 clues and 2 walls to completely determine a grid, but the path rule really is that restrictive.
Glad to see Marty's continuing the joke of having the rats start right next to the cupcakes.
on 21. May 2026, 00:28 by giocanessa
Absolutely unbelievable puzzle. I found it easier than the others, but no less brilliant. Regarding the book idea, for the FOW sudokus, I was thinking you could use scratch-off coating, like the material used on scratch cards. Next to the puzzle, there could be a legend indicating which squares to scratch off after entering a number, with the solution printed at the end of the book to make sure the player doesn’t scratch something off randomly after making a mistake. The only downside is that this would make the puzzle usable only once. A more reusable alternative could be to use black removable stickers instead: the player would peel them off when a cell is revealed, and potentially place them back later to reset the puzzle.
on 20. May 2026, 23:51 by davidz32z
Cuttttteeeeeeeeeeeee <3<3<3
on 20. May 2026, 23:11 by Christounet
Funny that there is still a color as "basic" as yellow at this point. I guess it makes sense because yellow = green + red. Or is that just random ? Or maybe you set that one a long time ago and the color remained...
Anyway, really impressed this grid exists at all!
And now you can add the "plush rat" to the "rat run" shop, smart move :p
Marty: see my reply to mir85 below :)
on 20. May 2026, 22:38 by monsen
Another great puzzle. Quite a bit easier than the other recent entries.
on 20. May 2026, 22:08 by AshBrown
Another great one. After failing the last 2 its good to be back.
on 20. May 2026, 21:46 by osmie
Echoing the previous comment about a book. If you'll let some random Internet stranger leap in with an idea about printed FOW, one could put a non-sequential numeric code into the upper right corner of every cell that reveals something structural (plus a smattering of cells that don't), and have an appendix which jumbles up all of the codes for all of the FOW puzzles, in numerical order, intermingled with an equal number of decoys. Then any solver who enters a digit into a coded cell can check the appendix, learn "R3C1 is a 9. R8C4 has a green line entering above and exiting below" (or what have you), and not be spoiled by the adjacent clues.
on 20. May 2026, 20:17 by mir85
Very nice! When I first looked at the grid it just seemed impossible that this could have a solution. Quite interesting how the german whisper and parity combo works.
Is there a reason this maze is yellow? You said you had been saving yellow.
Marty: not particularly, except that I made this puzzle a very long time ago, while I was still making season 2. Yellow is quite a light colour so the walls don't contrast as well as other colours against white. But I wanted to use yellow for one of the puzzles, and so this one seemed like the best choice because it hardly has any walls anyway. :D And so I made it yellow when I first set it, and I really liked it and became used to it until it would have felt utterly wrong to change this to another colour
I see, thanks! It does look stunning :)
on 20. May 2026, 16:09 by Franjo
Hard to believe that this can exist - but here it is! Another incredible setting from the master. Thank you!
on 20. May 2026, 16:06 by Tumbo
Lovely as always Marty. It's nice to start the puzzle and ask yourself is Finkz or Phinx going to get lucky and go directly to a cupcake this time.
on 20. May 2026, 16:05 by GeorgeTheToad2
Another beautiful maze with lots of sudoku to do. I can see why Simon is on a plane today! The story is getting exciting too. Thank you Marty for another colourful maze.
on 20. May 2026, 15:21 by Prince Joffrey
Someone has got to do some Sudoku in a Sudoku puzzle tonight - unbelievable
on 20. May 2026, 13:45 by mscha
First impression: the rules aren't restrictive enough!
Second impression: the rules are too restrictive!
It turns out they are right in the Goldilocks zone. :-)
I was very tempted to use the title of the puzzle as an extra rule, but I managed to stop myself just in time.
Very nice puzzle, very satisfying how things just click in place once you figure things out. I think _someone_ is going to complain tonight about having to do too much Sudoku in a Sudoku puzzle, though. :-)
I'm both looking forward to and dreading the grand finale over the next two weeks...
on 20. May 2026, 12:42 by Nairurian
Who’s cutting onions?
What a lovely puzzle, it felt a bit overwhelming at first but as soon as I started thinking about what the constraint actually meant, it clicked and solved smoothly.
on 20. May 2026, 12:30 by cullenmersch
I have only just opened the puzzle, but this is by far my favorite grid so far. It is beautiful.
on 20. May 2026, 12:03 by Lykrast
Impressive how that one clicks together once you figure it out, especially considering how the maze looks. It did take me a while to find the last click at the end tho, but very nice.
Also what's that rat plushie on the picture? It's so cute I kinda want one...
Marty: that is Elliot's present for Zoe :)
on 20. May 2026, 10:33 by jobs2554
The grid looks very intimidating but the parity/german whisper constraint is that limiting. Very cool puzzle. If my guess on what the next puzzle is going to be is correct, the next puzzle is going to be very interesting.
on 20. May 2026, 06:22 by Fool on Hill
Not the hardest, but incredible minimal clueing for such a cleanly solvable puzzle
on 20. May 2026, 04:44 by SlimeIB
More like a traditional sudoku with a little ratrun-like restrictions.
on 20. May 2026, 04:19 by hamosphere
3* I feel... easier than last week's!!
on 20. May 2026, 03:53 by etoler
For me, this might've been the most intimidating grid of any Rat Run so far. And then I thought about it for a second, put the pieces together, and it suddenly just worked. Marty, I don't know how you do it, but I'm so happy you do.
on 20. May 2026, 03:12 by Douglass
Sublime as always, and one of the most effortless rat runs in my opinion! A perfect 3*
on 20. May 2026, 03:11 by QuiltyAsCharged
A connecting principle
Linked to the invisible
Almost imperceptible
Something inexpressible
on 20. May 2026, 02:41 by Angara
Big finale is close!
If you ever release a "Rat Run" printed book, I would definitely buy a few for my collection and as gifts for my nephews and friends who don't know about Sudoku. However, it's unclear how to implement FOW in a printed format.
Marty: aw thanks. Yes I have been thinking about the book idea, and the FOW episodes are the main problem. I could potentially just have the puzzles without the fog... obviously a lot of the cool fog logic would be lost, but the puzzles would still be solvable
on 20. May 2026, 01:14 by ViKingPrime
This is one of those Rat Run puzzles that will stand out in your mind, long after your solve is complete. Marty still has a few tricks up his sleeve for this final home stretch.
on 20. May 2026, 01:13 by mscha
Aw, that gave me tears in my eyes..
