The Basic Tips For Hard Sudokus 

I'm always so impressed with your logic. Your ability to wiggle out of spots where I reach a dead end is inspiring.

Managed to solve in 10:28 // Used both of the uniqueness tricks mentioned in the video, but the trick with the 1's was very elegant, and basically what opened up the puzzle. Thank you for another nice video!

These videos are great for offering much-needed encouragement when I've managed to fail on hard puzzles three times in a row.

The microphone had way more background noise than usual, so I liked the other one better.. Nice little puzzle though!

Loved watching this. Can you guys do a few more of these short hard puzzles as a little bonus maybe once a week in addition to the fabulous variant Sudoku’s that you do.

Solved it in 13m25s with pretty much the same start as Simon using that x-wing on 1s. Though I did manage to fill in the 3 in the middle right box as a naked single right away (not that it really helped much initially).

The sound is now more full and 'human and comfortable' than before. Thank You for the lessons and improvements and greetings from Finland !

Still some echo-y bits but without proper sound isolation such as acoustic plates or something like that, I think this is nearly as good as it can get! And saying this, I think it sounds great!

The sound quality is mostly fine... it's just obvious there's not much sound absorption in the room and that you're not using a pop filter. If you listen back to your video and focus on when you say the following consonants: S, T, P, and K (or hard C), you can hear what I'm referring to.

I think the mic is a better sound overall, but you may want to move it closer, it's picking up a lot of background noise. It might also be worth running a de-noiser of some sort, it sounds like you've got a gate going which means that background noise only comes in when you're talking which makes it harder to tune out.

Mic sounds fine but is too low.

Listening on studio monitors: the sound quality is vastly improved. The levels are a bit lower, but the noise floor is also dramatically reduced. Of course, that unmasks background sounds that the noise floor used to drown out. Without pulling the audio up to look at the levels, they seem reasonable, but your voice is much lower than your music. You may already be doing this, but if not, it's worth pushing up the gain until you start clipping, and then back it off just a hair. To match the music you may also have to apply some dynamic compression. Both things help people on portable devices with low output speakers, particularly if they're in a noisy environment. Too many devices can't get loud enough to make reasonable recordings intelligible.

Simon, your sound is fine and the echo has gone (never really bothered me to be honest). However, it sounds like you are talking a little softer as you may have been a little self conscious of the echo. I noticed that after coming from Mark's last video to this one. All good! Nice solve too :)

Your sound is usually fine to me but Mark's always sounds like he's recording in a tiled bathroom.

I like the previous mic but it might be just because I'm used to it. In comparison, this one has the volume a bit too low and it uses a bit too much base ... but it doesn't really matter as I'm interested in the content. Did you know you can set up a voting button on your youtube video? It's built right into youtube studio - not that I've tried it but I believe it's fairly easy to do. Again I enjoy yours & Mark's differing styles to solve sudoku, and I'd like to see more of you to attacking the same puzzle (a video each?).

first time I completed one of these completely on my own! Took just under 12 minutes. I saw that x-wing with the 1s pretty quickly. The rest was just a lot of re-evaluating columns and rows.

4:08 I am sorry to say this, but you are mostly looking for complicated solutions of cells (due to solving lots of hard puzzles) while you overlook the easy (basic) solutions... in the 8th collum you find two cells where can 3 be put in, but overlook, that in one of those cells cannot be any other number than 3 ...

A suggestion for the channel, weekly puzzle recommendations that you don't solve on the channel? Or possibly release a puzzle in the description and then later that week have the solve to help people identify where they are having issues with difficult puzzles? It would boost community interaction for the channel. Just a suggestion if you and Mark are still looking for them!

Thanks for all of your help on these videos. I watch them on my phone and have sometimes have a hard time hearing what you say because of my volume. I have tried volume booster apps but they do not seem to work on RU-vid.

I did it! First one of these I've been able to solve. Took me an hour.

Did this also with no uniqueness problems. Didn't even saw them as there were other ways to solve this. But I must say that when I spot one I always use it right away because why not when not making videos.

16:13 for me, I think I'm getting better already, thanks to this channel

New Mic does actually seem like it has better audio definition, but it is a bit low, might want to adjust some levels. Also investing in a good filter for a condenser mic helps keep all the random noise out.

Just trying to be real but imho this microphone sounds way worse compared to your old one (didn't really have a problem with that to begin with). There is a lot more kind of echo sound whenever you speak, I suggest going back to the old one or trying to improve the sound by adding a few plugins using VSTHost or something similar. (I'd just go back to the old one, really, it was fine) @edit: I want to add that while I think that it's worse it doesn't ruin the video in any way, once you get used to it it's also fine.

Thanks, this time I could see no error. Yes it can be useful to stick to 2 pencil markings of numbers. Instead of all possibilities, and clutter the box. I go and look around when I can find a tutorial of the various methods to solve the sudoku on your channel :)

The mic is fine. When I resolved the 9's I found that the right middlebox had a hidden three. With the 1's being partly resolved, the rest of the puzzle went quickly. You are right, it was an elegant puzzle.

After 2 days of trying, doing half, doing stuff wrong, I restarted it this morning with a fresh mind, and determination to finish it. Finished in 18 min but already knew the 9s had fixed places and some numbers had certain logics. So I think, if I hadn't been trying the past 2 days, I would have probably took 2 hours.

I noticed that the 3 when in the Middle Right 3 by 3 grid straight after I had put all the 9's in because it was a unique number.

The voice quality on the new mic is better, but you can very clearly hear every thump/click, louder than your voice. A mic boom arm ought to clear that right up. Depending on what mic you have, you can get one pretty cheap on amazon (

This is excellent (looks down at other commenters *vigorously nods agreement*) so many tips. Much help. Many thanks.

Always amazes me how you can instantly tell what the remaining numbers are for a cell. By the way, have you ever tried a Str8ts? Would love to see you have a go at one of those.

Mic is way worse. I never noticed anything wrong with the old one.

The mic sounds good to me - maybe just a bit too low though. I think a lot of the people saying they really don't like it might just have got used to the last one. At first I didn't like it either but by the end of the video I'd already started to like the new one! Your audio was never really an issue for me anyway though, so don't worry too much about it! Just keep up the great content!

I've taken a break from Sudoku and have been doing a lot of Str8ts recently and I think that has really changed some of my solving technique. I'm starting to spot stuff like naked quadruples. I solved it but not sure I solved it in the best way.

Thanks for this puzzle! I did have to up the volume on my laptop quite a bit to hear everything well, so that could use some fine tuning. Later!

This video is a must watch for somebody going from intermediate level to advanced

I'm such a newbie. I learned a valuable lesson today. I was able to boil the grid down to the same logic as Simon at the 14:30 mark when he finds the 4 he overlooked. I might miss things, but when I get stuck and go back to the video, my logic so far is usually about the same as Simon and he's usually pondering over what to do next. I had all the same pencil marks as him when he placed the 4 in row 9 at the bottom. Tried to solve and ran into the problem with the deadly rectangle as 2s and 5s interfered with the solution. Watched and thought "okay, something new to remember." Then I noted that and tried to go forward again. Three times I got an inconsistency tried again, and started over again. What's was going on? I watched closely and realized that when unwinding numbers in pairs scattered around the grid I can't be mixing block and cell logic. I need to unwind numbers that see each other or something can go wrong because some pairs are "virtual" probabilities (but unwind nicely when "seen" by another cell" and some are hard and fast where two cells in the same block contain one of two numbers. If I use information derived with one kind of logic, to unwind information derived with the other kind of logic, it can create a headache. Valuable Lesson: use cells that can see each other to resolve things as far as possible, or I might run into problems where a cell couldn't have even had a certain value in the first place.

I know you probably won't do videos of your sandwich sudoku app, but I'm stuck in one #36 I don't know if you have any tips for that or a video explaining a similar strategy.. also I have some review for your app if you'd like to hear it

When do you use the corner markings and when do you use the centre markings?

PLEASE make the corner pencil marked numbers remain in their natural position. So grateful for all your tips and techniques, thank you.

It seems like your microphone is so good, I can hear ambient noises like kids/music/talking more when you talk (as I can tell you are using voice activation over push-to-talk). Perhaps a post-process of the video to take out high-pitched/distant sounds or something?

Solved in 31:35! Though I know I can do better after watching how you did it, lol. At one point I think I used a finned x-wing, despite not really knowing how they work

Always enjoy these thxs very much,haven't seen a cryptic xword for sometime......regards

Haven't watched the video yet but this solved nicely and seemed themed with (finned) x-wing into x-wing on the same number a couple of times in a way that Snyder notation made easy to spot. Of course, I may have just missed easier approaches.

It would be helpful if you could mention *how* hard these puzzles are supposed to be. They seem to be medium at the worst assuming a 5-step scale of simple, easy, medium, hard, extreme

11:32 at that point you noticed the unusual rectangle and that 5 could not go in Columns 4 and 5 of row 2. So, why didnt you put the 5 in R2C2? Too easy?

Did it in 29:04. Getting better.

Finished with a 30:35, not too difficult, just needed to focus on the proper cells to distinguish the next step.

14:53 for me, not as hard as I thought it would be! Searching for almost complete lines was what did it for me, found some squares where I could only fit one number, then it was easier.

Nice use of columns and rows in this one. 20:45. Not too bad.

1:50 Strangely, I missed placing the 9. A pair of 1s was placed afterwards. Following that, I took a long time to commit a Simonism: I spotted a jellyfish in 1s. It forced 1s in two positions in the jellyfish in column 3. Following which, I noticed that I could have done that with the x-wing in 1s -- or with routine simple logic I used before I ever heard of "x-wings".

An interesting sudoku. I solved it using completely different logic. I missed the trick Simon found in box 9, but spotted 2 (or was it 3) X-wings and a Swordfish, which got me through the puzzle, albeit much more slowly than Simon.

I watch your videos on double speed and there’s a higher pitched whispy sound in the background that sounds like extra resonance or just picking up background noise, almost like you’re talking in a bottle. The mic seems like it’s pretty sensitive and perhaps picking up more than it’s supposed to. I don’t think it’s a mic problem though. Rather, it probably has to do with the audio recording settings

10.33, felt pretty good! Mic sounds good, although too low

Mic sounds fine. Might need to tweak the settings or setup to reduce the reverb

Simon = the best.

I did it in 37:14. It took me a while to notice the 1 x-wing in column 1 and 2.

What app do you use for your sudokus? I am trying to transition from pen and paper but dont know which apps are good 😅

The new mic is good, but it’s a bit too low

Did it in 33:17 without hints, but once again, without your videos, it probably would've taken me hours longer. :D

hmm, hadn't thought about the uniqueness technique. always annoyed me but i wouldn't have thought to use it on higher quality sudokus... though i'll admit to using it relentlessly on enigmas

Solved this one in about 40 minutes. I did pretty well up until the part where all the 3s were filled in and then got stuck for a while before finally finding the 7 in r7c3, and from there it was fairly quick to finish off. Completely missed the uniqueness constraints though. The app I use seems to have a lot of hard level puzzles that require uniqueness constraints to finish.

One thing I don't understand is about the "Deadly rectangle". I am sure I have seen you talk about the same type of pattern before, without the puzzles being broken. What is different here?

I think the voice sounds way calmer now, more pleasing to the ear

took me a bit to find the one pair but 21 minutes aint bad :)

Mic is fine. However, volume seems a bit low - but not sure whether that's due to your mic, or to my living right beside the detonation pit for the local "Guns-n-Grenades Club."

Haha well that's interesting, I missed that 4 resolving the 4-6 pair to finish it out for a few minutes as well. I actually probably spent 5-10 minutes enumerating the possibilities for all of the rest of the empty squares before I caught it though 😅

35:56 on my end. Not too shabby!

Thanks for the new mic! Sounds great! :)

11:53 You say that there can not be 5's but you did not explain why you picked the 5's instead of the 2's

34:07 I say this number with painful shame because over 25 minutes of this puzzle were spent finding absolutely insane logic until I noticed... I had mistyped a pencilmark. It then took just about two minutes to unwind the entire rest of the puzzle. FML.

3:38 for me after importing and building the list of candidates. Nothing more complex than an X-wing and a Type 2 unique rectangle, but still a good puzzle.

What software is being used here?

Finished in 21 minutes, should have been quicker but I placed a 4 in R5 where I meant to put a 3 and a few minutes later I realized the puzzle was broken.

Finish in 21:01

Sound is fine Simon but could you have a word with Mark, sounds like he's in an echo chamber :)

Cool bro

The sound quality is totally awesome. And another awesome lesson!

Keyboard sounds better with new mic .. could solve this one .. for some reason .. a breakthrough for me ..

soound is fine but its a bit quiet

Is there a name for that sort of pattern Simon starts finding a bunch of around 3 minutes?

Both of your mikes are fine, old mike had a little echo and picked up kids in another room but my house is full of kids and I can tune that out. New mike has no echo and no kids so get another of these and give one to Mark. I won't watch his videos because they always sound like he is recording in the bathroom so I am missing watching his solving talent.

29:23 for me. I somehow got stuck on the 2 at 7:36 that was staring right at me.

For basic tips you could go a little slower and explain your logic in more detail. Beginners like me try killer sudoku and often get stuck in the mire.

30m 12s

Day 4 of asking for dark mode 🙏

"Didn't notice that 6 in that row" You also didn't notice the 6 at R5C5 as you placed a 6 in R4C1. The TOP tip here should be to ALWAYS follow basic Sudoku whenever you place a number down.

It sounds so weird hearing Simon's voice in not-potato quality.

12:40 wow faster than Simon teaching, i found some naked singles so early

You know, I really hate you :-) I filled in the grid pretty much as fast as I could using the same logical steps you used and it took me about 20 minutes. You did it in well under 15 minutes, with narration, and with delays due to missing the bleeding obvious a few times near the end! How? I am convinced you have a way of making clocks run slower!

Love the new mic!

The new microphone is a huge improvement

3:45 yeah and thats how far i got after 8-10 minutes and how far i am still, 10min later. still a beginner, still learning a lot through every new video here, still not good enough to go on :(

My time 44 minutes. I'm getting under an hour more often now.

Took me about 50 minutes to finish the puzzle, but I'm glad I at least managed to solve at.

39 mins, man do I suck..solved it by using some forcing chains on the 1s.. terrible..