RAT RUN 33: Hot and Cold
(Published on 8. April 2026, 03:02 by marty_sears)
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, share cells, or pass through any maze walls.
HOT AND COLD ZONES: Divide the grid into two zones of orthogonally connected cells, one hot and the other cold. No 2x2 area may be completely in one zone.
INVISIBLE WALLS: A few maze walls are visible, but the rest are invisible and must be located. If two orthogonally adjacent cells are in different zones, a wall exists between them. If they are in the same zone, no wall exists between them. Because no 2x2 spaces exist fully within one zone, no diagonal movements are possible in this maze.
BOX BALANCE:
• The value of a hot cell equals its digit +1.
• The value of a cold cell equals its digit -1.
• In each 3x3 box, the total value of hot cells must equal the total value of cold cells.
CURRANTS:
• If a BLACKCURRANT sits between two cells, then the value of one is double the value of the other.
• If a REDCURRANT sits between two cells, then one has an odd value and the other has an even value.
• Two cells joined by a currant are both in the same zone.
TEST CONSTRAINT: In this experiment, Phinx must stay in the hot zone and Finkz must stay in the cold zone.
Solution code: Hot digits in row 5, from left to right
Comments
on 24. May 2026, 21:01 by jez9999
Really nice puzzle, I'm not usually good at mental arithmetic but for some reason this one's solve and sums came quite naturally to me and I felt like I was doing rather complex calculations and coming to quick results, once I got into the swing of it.
on 13. May 2026, 02:24 by Lykrast
Note to future me: don't do sudokus after midnight, especially those that involve a lot of checking sums like this one.
Was still a fun solve when I could think properly. Definitely an odd one compared to the previous rat runs, since you don't really have a constraint on the path itself and it's about finding the hot/cold zones.
Ouch poor Elliot tho, I wonder if he's ok. But with worsening burns that doesn't sound like it.
on 14. April 2026, 20:24 by blackjackfitz
Huzzah!
on 14. April 2026, 07:01 by treevor
Amazing puzzle, I made a spreadsheet to solve this one lol
on 12. April 2026, 12:13 by Lutterot
Amazing puzzle, but it took me ages to solve it. Forgetting about a general blackberry possibility cost me more than two hours. After that it went smoothly, but it took until halfway before I realised the temperature secret. I like that you include a notepad when the puzzle requires more of the solver's working memory.
Thanks a lot, Marty. This is easily the most enjoyable puzzle series I've ever come across. Every puzzle is unique and you manage to utilise the consequences of each puzzle's mechanics beautifully. I also love the story telling.
on 11. April 2026, 16:12 by Klausku
First thought looking at this puzzle on wednesday: „how on earth…, safe it for the weekend“. Today after a long think I found some very interesting logic and spotted a break in. And then it flowed surprisingly smooth. What a brilliant construction. Thanks Marty!
on 11. April 2026, 12:16 by JamesMeowriarty
This one was out of my reach, I had to watch Simon's video to me started.
on 10. April 2026, 02:50 by monsen
Another great puzzle. This series never disappoints.
But this was quite hard for me. Probably would have been a tad easier if I had figured out the secret of the hot/cold digits sum before I got almost to the end of the puzzle, could kick myself for that.
on 9. April 2026, 21:47 by madhupt
Super, super, super, super, super, super, super,….
on 9. April 2026, 15:33 by BG03
You guys can all see where this is going right? The final rat run #40 is just going to be a completely blank white square. We will have to construct the puzzle ourselves and then solve it. It would be the ultimate Marty thing to do. And he is perhaps the only setter who can pull it off!
It will also prove that Finkz and Phinx have achieved super human intelligence and have transcended into a higher plane of existence. A fitting end to this series.
on 9. April 2026, 04:10 by psams
Very fun, definitely required a few side notes!
on 8. April 2026, 23:30 by Asparagus
Yet again the word masterpiece seems an understatement - another stunning creation!
But now I don't know which I am looking forward to more: the aqua rat run or the next instalment of the story!
on 8. April 2026, 22:05 by DaniK
Wow, fantastic! I found this one particularly smooth and fun. Great puzzle!
on 8. April 2026, 22:00 by Christounet
Hot stuff.
on 8. April 2026, 21:15 by mir85
So good I solved it twice!
I love a good yin-yang sudoku and this was wonderful :) Nice little twist with the build-your-own maze.
on 8. April 2026, 21:15 by Dcs
Absolutely incredible! I found the solve path very intuitive, definitely my favourite in the series so far. 4* is usually quite intimidating but I found this as hard as I would usually find a 3*.
PS: Big fan of the note-taking section
on 8. April 2026, 20:36 by dinonugs
This was a tough one, but all the more satisfying to complete. Extensive Excel note taking occurred :D. Still, I somehow was able to complete it with very few mistakes along the way. Thanks!
Edit: Somehow I solved it without figuring out the secret referred to in comments below. That would have made things a bit easier!
on 8. April 2026, 14:02 by wuc
Wonderful sum idea. As a yy veteran it felt rather approachable. What a beautiful puzzle. The main deduction itself. Mindblowing.
on 8. April 2026, 13:42 by etoler
How does this still feel undeniably like a Rat Run??
Genius as always. Thanks for another amazing puzzle, Marty!
on 8. April 2026, 13:08 by luna_vale
Amazing puzzle!
on 8. April 2026, 12:46 by Exigus
Fantastic. And the story as well. Thanks!
on 8. April 2026, 12:37 by Franjo
Thank you so much for creating and sharing another wonderful episode, this time featuring an amazing arithmetical YY. Brilliant!
on 8. April 2026, 11:01 by mscha
Awesome!
This was another one of those where I thought I'd never be able to solve it, but after the first deductions, it was a surprisingly smooth solve. I'd even give it 3 stars for difficulty, if it weren't for the evil black dot in box 7...
Of course, drinking coffee out of a Rat Run mug made solving a lot easier. ;-)
on 8. April 2026, 10:59 by ViKingPrime
This might be the most clever entry of them all and that is indeed saying something.
on 8. April 2026, 10:48 by Rab3aron
Wow! Brilliant design as always, I feel like every week I say this one is my new favorite!
on 8. April 2026, 10:35 by Fool on Hill
Wow! No idea how you thought of that, but it comes together beautifully once all the pieces click into place.
on 8. April 2026, 10:29 by ThePedallingPianist
Hot.
on 8. April 2026, 08:25 by Gammon88
Another amazing addition to the series, loved it!
on 8. April 2026, 07:55 by Angara
Incredible puzzle! I was stuck for an hour until I reread the rules and realized that I had forgotten about the same sum in the box rule and from that moment on, everything went very smoothly. Thank you Marty!
on 8. April 2026, 06:11 by chinesemaster
Never thought yinyang and rat run could go so well together! That's exactly what a genius is capable of doing. Thanks a lot!
on 8. April 2026, 04:49 by Silverscree
A very fun puzzle, and very unique in this series due to the nature of the test constraint. I eagerly await experiment 34!
on 8. April 2026, 04:07 by emoney1374
Sometimes I wonder “how can this man keep doing it?!”, but every week Marty delivers. My favorite puzzle in the series
