A Sudoku With No Digits. Impossible??!

*** STOP PRESS: NEW MODULAR LINES SUDOKU PACKS ***

We've just released two packs featuring a new sudoku variant: Modular Lines. The base pack is available to everyone FREE here:

The Competition Pack, featuring 18 puzzles, is available to our patrons and you can find it by joining us on Patreon for as little as $2/month here:

We're extremely grateful to the team of setters behind these packs: FullDeck, Missing A Few Cards, JC Godart, jeremydover, Raumplaner and rockratzero. Thank you!!

*** TODAY'S PUZZLE ***
[Apologies for the scheduling error today which resulted in us releasing two videos at the same time. This will teach us for having the temerity to try and take a couple of days off! Hopefully some of you will enjoy this video for an unusual reason - if you go back to June 6, you'll find Mark solved the same puzzle. Many of you have asked how Simon and Mark's styles differ - well now you can see!]

Another sudoku today by the wonderful Joseph Nehme - this one is called Some On Some Off. This puzzle is hard to grade - it depends how quickly you spot the underlying ideas (and whether or not basic sudoku eludes you!). You can play the puzzle at the link below:

Rules:
Normal sudoku rules apply. Along a main diagonal (marked in blue) digits cannot repeat. Digits along an arrow must sum to the digit in that arrow's circle.

*** Our New App Is OUT ***
Our new app is OUT on App Store AND Android!! We've completely revamped the interface. Now you download the basic app free and you can choose to download additional content. So there's a FREE pack of puzzles by Prasanna Seshadri and a paid pack: DOMINO SUDOKU!!! Prasanna's free pack includes one puzzle for each variant of our existing apps (so there's a killer sudoku, a miracle sudoku, a thermo sudoku, etc). Domino Sudoku is a pack of 100 handmade puzzles (40 on launch, 5 added each month for a year) by some of the best constructors in the World: Phistomefel, clover, jovi_al, Christoph Seeliger, Qodec, Sam Cappleman-Lynes and Richard Stolk have all contributed sudokus!!

The app is coming very soon to Steam as well.

*** Warm & Nerdy Merch ***

▶ Contact Us ◀

Twitter: @Cracking The Cryptic

Our PO Box address:

Simon Anthony & Mark Goodliffe
Box 102
56 Gloucester Road
London
SW7 4UB

(Please note to use our real names rather than 'Cracking The Cryptic'.)

▶ SUDOKU PAD - Our New App ◀

It's OUT on Windows (released yesterday!) via Steam here:

You can now input your own classic sudoku puzzles into our software using our new App! The app also comes with 12 handmade puzzles from us and we're also releasing occasional bonus puzzles too. Already available on IOS and Android.

**************************************************************

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[josephnehme]

Thank you Simon for the lovely solve. It's nice to see this one get solved by both you and Mark :)

[emilywilliams]

I started this video with quite a bit of curiosity, because the puzzle looked kind of familiar to me. I wondered if I had solved it on the discord server or something. Then I read the description and saw that Mark had posted a video last month of this same puzzle. Fascinating! So I settled in to watch Simon, and then I went over to re-watch the Mark video of this same puzzle. First, about Simon's solve, I really enjoyed it. I love that the logic seemed very interesting (to Simon, and to me), and that the puzzle seemed to present some nifty opportunities for non-trivial deductions yet was not too awfully hard. And as usual, I love to watch Simon explain and solve things like the contents of the arrows emanating from boxes 1, 9, and 2. So instructive. Thanks for this excellent video, Simon.

Now to a couple of comments about the two videos, the one by Mark last month and this one by Simon. Totally interesting that the approaches and the pathways through the solves were very similar, and so were the times to complete. Both colored 1s and 2s early on and used that info to deduce some interesting digits, and even the order in which the arrows were considered was almost the same. I think that is a tribute to the excellence of the setting, actually, as it shows that the constructor had in mind a logical path and was able to lead the solver to discover the right things at opportune times by how the puzzle was put together. The Mark video was one of the ones where I laughed out loud at Mark several times because he is very witty, and in this video by Simon I felt that Simon was more low-key than usual. But both were very interesting and engaging to watch, and the puzzle, of course, is very interesting and provides a lot of scope for good deductions. So, whether it was intentional or not, I very much enjoyed the dual solves of the same puzzle. Thanks for posting them both and drawing our attention to the duplication. So good!

[johnstipec]

Hello Simon. I am a fairly new watcher. (Maybe the last 8 Fridays)? An avid Sudoku solver at a “Hard” level. Likely capable of much more. Sorry I have yelled at you multiple times watching your solutions. (My wife actually videos my reactions to your solves). You are bright, personable and inspirational. I will attempt some of your puzzles soon as we finally moved to a spot with good internet and much less commute time. Thanks for making this game more. Cheers

[inspiringsand]

Rules: 01:17
Let's Get Cracking: 01:50
Simon's time: 25m28s
Puzzle Solved: 27:18

And how about this video's Simarkisms?!
Ah: 8x (03:20, 12:20, 15:56, 15:57, 16:00, 23:33, 26:50, 27:11)
Lovely: 5x (04:47, 05:55, 18:03, 23:41, 28:13)
By Sudoku: 5x (16:01, 16:23, 20:50, 24:47, 26:54)
Good Grief: 2x (09:23, 10:17)
Goodness: 2x (12:23, 25:47)
Clever: 2x (08:06, 27:21)
Hang On: 2x (08:50, 17:41)
Think Harder: 2x (13:23, 14:42)
In Fact: 2x (16:06, 16:16)
Progress: 2x (18:10, 18:32)
Sorry: 1x (14:38)
Out of Nowhere: 1x (21:10)
I Have no Clue: 1x (00:42)
Beautiful: 1x (00:29)
Come on Simon: 1x (09:09)
Of All Things: 1x (11:09)
Propitious: 1x (20:01)
Obviously: 1x (18:46)
Wow: 1x (09:02)
Losing my Army: 1x (23:58)
Have a Think: 1x (19:55)
Pencil Mark/mark: 1x (20:54)

Most popular digit and colour this video:
One (56 mentions)
Orange (21 mentions)

Antithesis Battles:
Low (7) - High (1)
Even (2) - Odd (0)
Column (6) - Row (2)

FAQ:
Q1: You missed something!
A1: That could very well be the case! Human speech can be hard to understand for computers like me! Point out the ones that I missed and maybe I'll learn!
Q2: Can you do this for another channel?
A2: I've been thinking about that and wrote some code to make that possible. Let me know which channel you think would be a good fit!

[rpnewlin]

Simon, it is joy to spend the hour or so a day I spend with you working through the daily puzzle. A pure joy.

[chocolateboy]

I finished in 64 minutes. There was a lot of fun logic here regarding the arrows and diagonal lines. It was a lot of fun to calculate in my head the different possibilities of 89s. I finally cracked it with r7c2 and r3c4 being the same and unable to both be 2. I enjoyed this one. Great Puzzle!

[santisis]

I started to solve it and it was like a deja vu increasing over the solve. Ten minutes into the solving I have an urge to browse the channel history to confirm if that was the same sudoku I've solved one month ago or no. And yes, it was.
I'm surprised of my good logic memory remembering the same steps.
Last time I was nearly 60 minutes with this puzzle.

[HunterJE]

6:50 There is a way to limit that arrow more at this point - because of the 12 pairs in rows 2 and 3, the second 12 in box 2 has to be in to row one, where it can only be r1c4 and creates a 12 pair in column 4, which therefore gives r5c4 a minimum of 3 and the arrow sum a minimum of 7

[santagonewrong]

A simpler way to make progress from where you were at 5:07 without needing to do the whole colouring 1s and 2s thing - because only one of the top circles can have a 9 in it, there's 1 degree of freedom between those arrows combined. And it has to be in the 1-2 pair in row 3, which immediately removes the possibility of the degree of freedom being anywhere else.

[laszloliptak]

Excellent puzzle. Solved it in 33:33. At the beginning one can quickly limit the digits on the arrows in boxes 1 and 2 by observing that there is a combined degree of freedom of 1 on the two arrows (as only one of them can add to 9), which is used up by the cells r3c4 and r3c7 (only one of which can be 1). So every other part of the arrows must be minimum, placing 3 in r3c2, 1 in r4c3, and a 34 pair in r12c6.

[kevinmartin]

Around 13:00, cleaning up the 8/9 pair in the top row is quite simple if you just total all the cells on the two arrows. Totaling up the minima, you get 3+4 in column 6, a 1/2 pair in each of rows 2 and 3, 3 from R3C2, and 1 from R4C3, for a total of 17. The sum of the two arrows cannot exceed 8+9=17 so all the values in column 6, R4C3, and R3C2 must have their minimum values. R1C6 and R2C6 are a 3/4 pair, R3C2 is a 3, and R4C3 is a 1.

Which is the 8 and 9 toggle on which way the 1/2 pair turns out in row 3.

[jakobpbengtsson]

Was stuck a long, long time until I found the same trick for solving r1c5, and then stuck for even longer due to accidentally putting the numbers on the wrong places for r1c6, r2c6.

Lovely puzzle (and as someone who isn't that great with more advanced sudoku, this hit the right spot in that regard), and a great video as always. Thanks Joseph for making it and thanks Mark & Simon for making the video!

[SnowTheJamMan]

Well we finally got Mark and Simon solving the same puzzle

[stevieinselby]

12:40 - that's a bit of a convoluted way of saying that the 8-9 pair in row 1, with each arrow having a maximum of 1 degree of freedom, actually means that the two arrows _between them_ only have one degree of freedom (because they can't both be 9), and _the 1-2 pair in row 3 uses up that degree of freedom_ and so everything else has to be minimum.

[nirmalasokan]

At 5:45, you can eliminate 4 from R3C2. If the digits in box one were 1, 2, 4 then that would make the circle in R1C2 9, with the rest of the arrow digits being 1s. But if that were the case, that would force R2C7 to be 2 and the circle in R1C5 would also have to add up to 9 which is not possible because it would see the 9 in R1C2

[th.nd.r]

That was lovely! Cool setting and solving, my general impression is that you are correct about the difficulty, I thought it was super clever and satisfying to see each of those little releases in the pressure of the puzzle with every difficult/surprising deduction! Also, you forgot to give the 3 in the corner its song!

[gunterbosman]

Since a couple of weeks I've been finding my way to solving these kinds of puzzles. I'm totally hooked. This one took me a bit more than an hour to crack, but everytime it's just such a beautiful puzzle. I wonder when I will grow tired of them. :p

[heatherfyffe]

Took me over an hour and a half but I got it! I was falling asleep for part of that time so that probably slowed me down haha... I took a break and finished it when I was awake. I got along quite quickly at the start, then was very stuck for a long time, finding only little breakthroughs here and there that didn't seem to get me anywhere. Finally I got a major breakthrough when I finally disambiguated all the 12's, and from then on the rest of the solve was lickety split a piece of cake. NOW I'll watch the video and find out what painfully obvious trick I missed that would have saved me an hour hahaha

[alienrenders]

18:17 for me. Hadn't done sudoku for a while. I think I landed on a great puzzle to start up again.

[R.Daneel]

Let's just give Simon a hand for wearing that fleece hoody when the temperature there was recently close to 40C!
I'm surprised he wasn't noticeably smaller at the end of the video.