Invisible Thermometers: A Game-Changing Sudoku

*** TODAY'S PUZZLE ***
So many of you have requested that we attempt this puzzle, Invisible Thermometers by Nahileon. The ruleset seems completely ludicrous - who would come up with such a thing?! Well it turns out that, yet again, Nahileon has produced something utterly mind-blowing. But it is quite hard ;)

Play the puzzle at the link below:

Rules:
Place the digits 1-8 once each in every row, column and region. A digit in a cell with a circle must be odd. A digit in a cell with a square must be even. There are invisible thermometers in this grid. Every empty cell (the 6x6 in the center) gets visited by one of those thermometers. Digits on a thermometer increase from the bulb on one end to the tip on the other end. The thermometers are orthogonally connected and don't fork or overlap. A thermometer may have length 1 if it's bulb and tip are the same cell. The difference between bulb and tip must be unique for each thermometer.

*** NEW SUDOKU HUNT INCOMING TOMORROW ***
A new sudoku hunt, The Planets Suite, will be released tomorrow at 4pm UK time on Patreon. It's one of our own and should be slightly easier this month. Well done to all of you who solved DiMono's Jewels Of Osiris hunt this month - watch today's introduction for details on the best entries (and the outro for the roll call of all successful solvers.)

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▶ Contents Of This Video ◀

0:00 Theme music & intro
1:20 Happy Birthday
2:12 The Planets Suite - new hunt tomorrow
2:35 Rules
6:25 Start Of Solve - Let's Get Cracking!

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You can input classic sudoku puzzles into our software and help support Sven, the programmer responsible for the wonderful user interface we all use to play these puzzles everyday. The app also comes with 12 handmade puzzles from us:

iOS:

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ALSO on Amazon: Search for “SudokuPad”

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[nahileon]

I was a bit worried, when I saw this puzzle appear on the channel. I thought it was extremely difficuIt and maybe too much for a solve on camera. But of course Simon killed it!

[alexanderzippel]

My man is out here solving a blank sudoku with one of the most complicated rulesets to wrap ones head around and is apologizing because he needs time to think. You have my respect for just solving this sudoku but the fact that you try to appease the 0.01% of people who are able to advance faster than you is just such a nice touch.

[ryxiewuff]

You said at one point that if you weren't making a video you'd have whipped out pencil and paper and taken notes about the thermos - I can't speak for everyone, but personally I would love seeing stuff like that in future videos, either via a document reader or some MS Paint doodles. Doesn't much matter if it's a bit janky, it'd still be fun in my opinion!

[deniseiln]

Simon, please do NOT make me glare at you over the internet. The fact that you were able to solve this at all without using pencil and paper to sketch out possibilities... is amazing. The polar /opposite/ of "too stupid".

You're dealing with a technical issue: you need to have a way to write things off the grid and have them be visible. Whether this is a notepage file that you drag into and out of frame, or a piece of paper with a second camera (possibly your phone?) pointed at it... either will work.

When you have a moment, please see if there's a way you can work with the tools that work for you. (And yes, that's easier said than done, I know.)

Because we also enjoy your comments about the puzzle and the solve - especially when they're kind.

And that includes you being kind to yourself.

[mrmckenzie]

I was able to easily solve this puzzle in under 20 minutes by staring dumbfoundedly at the blank grid for 19 minutes then skipping to the end of the solve and copying Simon's solution.

[TPunkt]

Hey guys,
I am the 40-year-old Thomas mentioned at the beginning of the video and I am proud that I got my own "Happy birthday" section in one of your videos. Many thanks in particular to my brother Martin who apparently made this possible. I am touched. However, I am still waiting for the promised chocolate cake. ;-)

Simon and Mark, please keep up the fantastic content. With your logically comforting manner, you are a real enrichment for the stressful everyday life. No matter how long your videos are. ;-)

Many greetings and thanks again,
Thomas

[curufinwefeanaro]

6:46 "...and that is because 'O' and 'orange' begin with the same letter."
One of my favorite knowledge bombs!

[patrickgass]

I watched it happen and I still couldn't really tell you what happened... a remarkable puzzle and a well-earned solve by Simon. Wow

[selenasilverstep]

I was just solving this puzzle recently and thought "this break-in is too difficult, probably won't see it on CTC" so kudos to Simon who did the impossible I guess. time to dig in!

[imanhaiqal]

Very nice solve Simon ! Next time when you’re attempting such puzzles, please use a notepad (or excel etc) for you to keep track them (and not just try to memorize them all). It’s easier for you and for us viewers to visualise all that.

[slapusillydawg]

1:15:00 I don't like when simon is so hard on himself for missing something :(
you aren't stupid simon you are brilliant

[ElCheezus]

1:38:34 My path through this was:
- The F in column 2 requires an adjacent 7 on its thermo, so R8C2 can't be a 7.
- This puts a 7 into R8C6, since the corner is already ruled out.
- Now you consider where F goes in C7. Since F requires an adjacent 7 on its thermo, F can now only be in R3 and connects to R2C7

[AvatarOfEntropy]

I kept hoping Simon would notice that his 4 8s logic applies to all the even digits. So that means that his 4 odd thermos need to start with 1s so you can put 4 2s in the puzzle (except the 1 cell thermo)

[rosiefay]

0:55 This immediately makes me think that, because 36=1+2+3+4+5+6+7+8, those are the thermos' lengths, and their differences accordingly 0, 1, 2, 3, 4, 5, 6, 7. ... And I see that Simon thought the same. But gosh it became practically unsolvable from there. Simon, I admire you for your solving ability and your patience to stick at this beast for nearly 2 hours.

[tiemen]

1:15:00 I felt for Simon here, as this was literally one of the first deductions I made before even writing in any numbers.
After realizing the four 8's on thermos are 1-8, 3-8, 5-8 and 7-8, you can also similarly deduct that he four 2's on the thermos must be 1-8, 1-7, 1-5 and 1-3. So you immediately find the distribution of all the thermos except for the single cell. The single cell is odd, and is either 1 (which we have so far used only four of on our thermos), or whatever duplicate occurs in the corners.

[selenasilverstep]

for anyone who did not enjoy the 10-minute bifurcation chain, I have a gift for you! at 1:23:35, what Simon failed to appreciate is that r3c6 is now a C, and C must be connected to 3 and D, but r3c7 can be neither. by the same token, C is also not in r3c7, and must be in r3c8. you can attempt to solve from this point.

[PuzzleQodec]

Haha this is amazing! It's the puzzle I did not dare to recommend because I imagined Simon being stuck and sad.... and then he solves it anyway! I'm looking forward to the next hour and a half. :)

[adamanhavengarde]

at around 27 to 30 minute mark, Simon has deduced a 1-8, 1-7, 3-8, 5-8 and 7-8 thermos. If there are four 8s in the sides, there are four 8s in the middle. This is the same for all other even digits. The above given only shows two 2s and three 4s and the only way to get both 2s is adding a 1-5 and a 1-3 line, leaving only the single box thermos unknown.

[morningplum]

I know it's been said several times but watching you figure out those possibilities without pen and paper was amazing! And your ability to explain it in a way that is both interesting to watch and understandable to the viewer is phenomenal. The logic of this puzzle has been one of a kind for sure and you cracked it! Well done!

[brettduffin]

Love it how Simon prefers to look at the screen in his mind above the monitor rather than the monitor! He is seeing his puzzle in the air.