Table of contents
- Braving a freezing summer day to tackle a mind-bending puzzle—let's dive into "Holand" by Fistofel!
- David, wishing you an amazing birthday filled with chocolate cake, and best of luck with your wedding and house renovation next month!
- Solving puzzles is about connecting unique shapes without breaking the rules—let's get cracking!
- Every wall segment in this puzzle must be at least size four to contain a tetromino.
- Every gray section in the puzzle must touch the single green tetromino to form a complete orthogonal connection.
- Understanding tetromino tendrils in puzzles: the maximum number of connections is capped at four, but strategic placement can push it to five!
- When solving puzzles, sometimes you need to think outside the box—like finding that fifth tendril!
- Solving puzzles in the dark while battling the worst weather—dedication at its finest!
- Solving complex puzzles often requires blending logic with intuition.
- Solving puzzles often means finding the right connections and avoiding walls that split your progress.
- Creating a wall in the grid to separate sections is key to solving the puzzle.
- Solving complex puzzles requires patience and creativity; don't give up when it seems impossible!
- Solving complex puzzles is all about recognizing patterns and connections.
- Just solved one of the most mind-bending puzzles ever, felt impossible but nailed it with pure logic!
Braving a freezing summer day to tackle a mind-bending puzzle—let's dive into "Holand" by Fistofel!
Hello and welcome to Thursday's edition of Cracking the Cryptic. On this freezing cold day, I've had to put a jumper on. It's ludicrous; it's meant to still be summer, isn't it? Anyway, that's the weather. What are we doing in today's video? Well, I'm going to be trying a puzzle for you. I say trying because it is a Fistofel puzzle called Holen Holen Still, which is clearly German. I guess it might be "hole," and the puzzle has some sort of LITS element, which is a logic puzzle. I'll explain that when we do the rules, and that's a reversal of LITS. Basically, I've got no idea what the puzzle title means, but lots of you have requested this, and you know me, I absolutely love Fistofel's puzzles, so I'm going to have a go at this. It's No Soku. The eagle-eyed amongst you will note that the grid is 10 by 10. The rules are bonkers, so I'll read them to you in a moment.
Before I turned on the webcam, I went over to Logic Masters Germany and snipped some comments, which I think explains why we're getting a lot of requests to have a look at this one. Mark Sweep, who's a brilliant constructor and solver, said it was simply awesome. But Naria's comment struck me as very daunting: "After understanding the core implications of the puzzle, I think it is more intuitively solvable than purely logically." That is terrifying. Jesper, one of the cleverest men probably on planet Earth, just writes, "Lovely, thanks." Anyway, this is what I'm going to be having a go at, and I am very much looking forward to it.
A couple of things to mention before we kick off and I read the rules. First, thank you so much if you joined us for our stream last night. Mark and I returned to streaming after a hiatus during the summer. We were streaming a game called Crypt Master, and it was very, very strange indeed but quite a lot of fun. A bit terrifying—the typing got—you have to be quite quick at typing in order to not get killed by the monsters, and I proved to be inadequate in some instances there. But anyway, it was a lot of fun. We will be streaming again probably the same time next week. Keep an eye on your notifications if you do like to watch a stream.
Other than that, over on Patreon, we have our Hollywood Sandwiches competition running. Do check this out. Lots and lots of you have been managing to solve all of the puzzles in this hunt now, especially since we published a hint. If you are stuck, we didn't mean to, but puzzle one is quite hard. Sometimes it is quite hard to get the gradient of the difficulty correct, and we made puzzle one a bit too difficult this month. There is a hint over on the Patreon chat channel on the Discord server that should help if you are stuck on that one. Otherwise, just enjoy the puzzles. We think they're a bit of fun, and the feedback has been great. That's a competition running until the 20th of September over on Patreon, which is our Sudoku club. Actually, although there are a lot of bonus videos there, there are crossword bonuses, Mark's connection videos, my lengthy solves, including some very lengthy solves of Fistofel puzzles—they all live over on Patreon. It's a couple of bucks a month to join us. Check it out if you're interested.
David, wishing you an amazing birthday filled with chocolate cake, and best of luck with your wedding and house renovation next month!
David, I understand that you are preparing for your wedding next month and also renovating an old house, which makes you quite busy. However, I hope today involves chocolate cake and that you have an absolutely brilliant birthday. Best of luck with the wedding and the house move in the near future.
Now, let's move on to the rules of Holand by Fistel. The rules are as follows: shade some cells in the grid such that all unshaded cells (the inside of the cave) are orthogonally connected to each other, and all shaded cells (the walls) are orthogonally connected to the edge of the grid. To clarify, if cells are orthogonally connected, it means they share a big edge. For example, two cells are orthogonally connected if they share a big edge, but not if they only touch at a point. We could make two cells orthogonally connected by including an intermediate cell.
In this puzzle, there will be a cave that must be orthogonally connected, and unshaded cells that have to connect to the edge. Clues are unshaded and indicate the number of unshaded cells seen in the four orthogonal directions, including itself. Shaded cells obstruct vision. For example, the number eight in the grid means it sees eight green cells, including itself, in the four directions.
Let's consider an example with the number eight clue. If the eight clue sees five cells vertically and three cells horizontally, it would constitute a valid configuration. The walls of the cave fence it in, adhering to classic cave rules.
However, we are not finished there. After solving the cave puzzle, the cave and the walls each form a region. These regions are used as the basis for a Litz puzzle. In this puzzle, you place one tetromino into each region. No two tetrominos of the same shape may share an edge, and reflections and rotations count as the same shape. Additionally, all tetrominos must form a single connected area, and no 2x2 area of the grid can be completely covered in tetrominos.
Solving puzzles is about connecting unique shapes without breaking the rules—let's get cracking!
For illustration, let's imagine dividing the grid into regions. Each region must contain a four-cell tetromino. For instance, if a region is defined, you might place a tetromino like this. You must ensure that all tetrominos are connected and that no 2x2 area is completely covered.. Let's go to the line drawing tool, so it might be something like that. That is a tetromino, and then you have to make sure that overall, all of these tetrominos are connected.
Let's do another region. Ignore the numbers for the purposes of this. Say that was another region. Because we need all the tetrominos to be connected, we could maybe have—oh no, but then we can't have 2x2s. You could have that, for example. You can see that this sort of S tetromino is not the same shape or Z tetromino is not the same shape as this L tetromino. Let's do another shape just to make sure that we're on the right track. Then we could have a shape here, and I was going to put an I in there, but I'm not going to put an I down there because then it wouldn't connect out. So, I could have that shape, and then there might be another region here. This could have—let's extend that there—then this could be an I shape.
Overall, our job is to make sure these tetrominos firstly, no two tetrominos of the same type touch one another. For example, if this one had looked like that, it would be against the rules because these two tetrominos are the same shape. This top right one is just a reflection and a rotation of this one, so that's not allowed. We've got to make sure that all the tetrominos form a single connected area, and no 2x2 area of the grid can be completely covered in tetrominos.
I think we're just going to have to explore this as we go. Do have a go, though. The way to play, it's only got three stars out of five for difficulty, which is perhaps the strange thing given especially Naria's comment. But anyway, the way to play is to click the link under the video. Now I get to play. Let's get cracking.
The first thing we can do here is that we're told that all of the clues in the grid are part of the cave. They are unshaded. This is very annoying because the thing about unshaded threes, for example, separated like this is if you were to make that unshaded, you make these beautiful three-length regions, which would then be fenced in. Look, all of those look very joinable together.
What about this eight then? That's often the place to start with cave puzzles. Start with the biggest number and see what we can say about that. Vertically, this cannot take more than five cells because it either joins to this five like that, in which case it would be capped out at five by this clue, or it never touches this five, in which case it could take those squares, and there are five of those squares. This eight clue must take an additional three horizontally, which means it must take this cell because even if it takes those two cells, it still needs one more. So that's definitely part of the cave.
Every wall segment in this puzzle must be at least size four to contain a tetromino.
Horizontally, the seven clue can't bump into the three clue, but I don't think that there's going to be an issue. The seven can't go to there. I'm not even sure if this is going to do very much, but I've just noticed something, so I'm going to tell you. If the seven did go all the way to here, I think these threes are now a problem because we can't join them up. Obviously, if we join them up now, this three would see one, two, three, four. If that's green, this sees four, and that sees four, so that would be gray, but I can't put a tetromino in that is too small. Let me just go back to the instructions. I thought each region of gray that we know has to get to the edge and has to contain a tetromino, as how I read the rules. No tetrominos, yeah, yes, I think that's right. So, I don't think you can have a one-cell piece of wall. Each wall segment that we're going to build in the puzzle has to be at least size four in order to contain a tetromino.
So, we can't go here, which is five, one, two, three, four. Now, we can go to there. I think we can't even do that one because that's going to give us the same problem. This then has to be green; otherwise, it fences something in and that breaks the world. So, we could take four maximum horizontally with this, so we have to take three more vertically, and even if we took that one, we must take those two. There we go, that's a tiny deduction.
Oh dear, I don't know. The problem is with things like cave and lit is I do them once every six months, and that exposes me to ridicule. I think the six clue, 87, the six clue is the next highest clue, and that looks like it can't take... Well, it can't bump into the five, can it? Well, it could bump... No, no, it can't. It would be six if it bumps into the five. So, okay, so this square, yeah, this can't be a gray square because then in order for this to achieve a tally of six, it's all horizontal; it's bumping into the five and breaking the five clue. So, that's definitely a green cell, right? And neither of these can now be gray, can they? Because there would only be two cells of gray, and we know each gray region or wall section we build is at least of size four. Right, there we go, there's something. A three is finished vertically, so we can fence it in with gray. That's the first actually meaningful deduction.
Now, this square has to escape because it must. This region here must be at least of size four. The six is now done; it only sees three, so it must see another three horizontally. Therefore, this square is not green; that must be at least of size four. Here we go, here we go, we're off and running at last. The five can only get four horizontally. The weather is horrible; that therefore must go up, which joins it to this. So, one, two, three, four, five could go as high as this, or it has to go horizontally.
Oh golly, okay, this has to grow, but I don't know how it grows. Oh, I'm sorry, I haven't got anything now. Let's just try and take stock. Where are we up to? We've got a six here which is finished, a five here which is not finished. These are separate wall sections, aren't they? That must be true, or you're going to get some sort of yin-yang problem. What do I mean by that?
Every gray section in the puzzle must touch the single green tetromino to form a complete orthogonal connection.
What I mean is that we know that all of the cave, which is the green area of the grid, connects to all of the rest of the green area. So somehow, all these green cells are going to amalgamate and be orthogonally connected. If this gray area and this gray area join up, you can see immediately this green area can't connect to the other green area.
Well, that actually is quite interesting as a thought because that means that all of the gray areas in the puzzle are going to have to meet in some relatively close area, aren't they? Hang on, because we're going to end up with a puzzle that's going to have gray in the perimeter, the walls, and those walls are going to extend wherever they extend but they aren't going to meet up with other walls.
What I'm trying to articulate very poorly is that the green area of the grid only has one tetromino in it because it's a region, but the gray areas don't connect with one another. So the way that we're going to achieve an overall connection at the end of the puzzle, where the tetrominos all join together through an orthogonal mesh, the green tetromino is going to have to provide the conduit to allow that to happen.
Every tendril of gray, and that's why I feel there's going to be an area of the puzzle—let's say it's here—because you're going to have a green piece of the puzzle. Let's say that had a tendril, and this was the point at which all of the junctions between the green and gray meet. All of the gray walls have to get to this point to breach it, to provide the bridge. Every gray wall section in this puzzle has to touch the green tetromino because there is only one green tetromino.
There can't be an absolute wealth of gray things. If there were loads of gray things, it's just not going to work. Imagine we have got loads of gray things, and each of these gray things was a different wall section. Then it's not going to work because these gray tendrils all have to touch the green conduit, and touch it in a way where they don't touch any other tendrils.
Here is another thought: you can't even diagonally join them up. If this was the conduit that acted as the way the gray tendrils performed, and then I sort of said this is a tetromino in gray, which wouldn't work, I'd have two eyes touching one another. In theory, that might work except look here: the green area must be green if we're saying that this tendril is different from this tendril. So, the premise is that there must be green between the tendrils, and the green between them needs to connect to the rest of the grid.
Understanding tetromino tendrils in puzzles: the maximum number of connections is capped at four, but strategic placement can push it to five!
When solving puzzles, sometimes you need to think outside the box—like finding that fifth tendril!
If one had an eye and that was a tendril, then this couldn't be a tendril, so that could be a tendril. One, two, these can't be now, so these could be tendrils. These can't be, so that... ah, okay. So you can get one more by having an arm. That's Bobin's worthy, isn't it? Because I thought we were going to be capped out at four. That's symmetrical in the sense that if I'd started by putting a tendril here, obviously those two couldn't then have been different tendrils.
I really like that logic though. I love the fact that if you put a tendril here and connect it to a green tetromino, that can't be a different tendril. By the logic we're discussing, these are different tendrils that must be green. Once I connect this tendril to the edge, wherever it goes to the edge, and this tendril to the edge, wherever it goes to the edge, that green can't get to the green on the other side. It's like a yin-yang argument.
So actually, let me just think about that again. Do we strictly... yeah, okay. If you did have an I tetromino in green acting as the tendril bridge, then the only way you can have five tendrils is with a strict on-off pattern around the edge of the tetromino. There are 10 orthogonally connected cells around the edge of the tetromino, and what we're saying is it is possible to put five tendrils in. The only way you could put five tendrils in and not touch another tendril is if they are strictly alternating. Otherwise, we're in a four-tendril world, and we've already found two tendrils, so there are a maximum of three other tendrils. Otherwise, we are overpopulating the grid with tendrils—not a sentence I thought I would be saying today.
There is a tendril somewhere there because that can't all be green without making this clue broken. So there is definitely a tendril somewhere there, but that doesn't have to be a tendril there. There definitely has to be a tendril somewhere here because otherwise, this three clue, if all of that is green, won't work. So we are now up to four tendrils. We can only have one more tendril. If we split the fours up, we are in tendril heaven.
You very nearly are already broken, actually. Well, not broken, but you do have to have a gray cell in one of those, but it could be that one and do this. If there was a gray section, look at this—this is very annoying. Let's say you did that in the top row. You're going to have to have something in this column. Otherwise, now that there are going to be five tendrils, one, two, three, there must be one here, four. Even if I connect those round, I can't make all of those green. So there are five tendrils.
Even though we've done very little of the puzzle, we do know that somewhere in the puzzle is the I tetromino in green. Sorry about this weather. I mean, what is the time? It is 2:00 in the afternoon, and it's basically dark. I don't know if you can tell that from the webcam, but it's basically dark. I am sitting here in the dark. Anyway, I was getting excited about tendrils. Even if all of those are gray for a single tendril, I can't make all of these green. So there must be another tendril in this column, and that's going to get me up to five tendrils. One, two, three, four, and something down there—five.
Solving puzzles in the dark while battling the worst weather—dedication at its finest!
In fact, hang on, those can't all be green; that's going to break the five clue. Right, so there is a tendril there. This is huge. Now, one, two, the weather is absolutely abysmal, but I'm so excited about this because now I've got my five tendrils. It's actually very difficult to populate column one at all because, oh, I see, they join up. That's okay. So, I think what we've proved now is because we're capped out at five tendrils and we know roughly where they are, there cannot be, for example, a tendril here because that would be a sixth tendril, and there is no possibility of connecting six tendrils through the green area. We have worked that out, so that is green. The same is true of these two squares; they are both green, and now the three is complete.
Okay, I know roughly where the tendrils are. I'm going to delete those gray tendril markers because I now know those are definitely gray. That gray is not of size four yet, so that's got to get out. This green has to connect to its friends, so it has to get out. These are finished in terms of these four clues. This has to get out somehow. The eight clue here could only take five vertically, so it must take three at least horizontally. So, it must take these. That's actually quite interesting because this little area here, this tendril, has to be at least of size four. So, that tendril comes out, and now this green area in the bottom has to get out, so it goes up there.
Can that be green? Very unlikely, because if that's green, then the area where the tendrils are all meeting is down here somewhere, and I think it's going to be right in the middle of the grid. Oh, well, I can't have any green there because if any one of these is green, these are two distinct tendrils, not one tendril, and I can only have one tendril around there; otherwise, I've got more than five tendrils. This three can't be a horizontal three because it'll bump into the seven and become a four, so that has to be green.
Now, this is some of the worst weather. Can you hear the wind? Sorry, I'm just sort of mesmerized by what's going on outside the window. The rain is coming down so hard. My computer is about a meter and a half from the window, and I'm slightly worried that the rain, because I've got my window open because it was meant to be summer today, might bounce so hard on the window sill that it will come in and hit the computer. I don't think it's hitting it at the moment, so I'll keep persevering with my tendril finding.
Solving complex puzzles often requires blending logic with intuition.
I want to say that if that was green, it can't connect to this without being four, so I'd introduce another tendril. I can't do that, so that's gray. There's some rule about 2x2s, isn't there? Can I have 2x2s in gray? Let me just read the rules again: Place one tetromino, no two tetrominos, all tetrominos form a single connected area, and no 2x2 area of the grid can be completely covered in tetrominos.
I was wondering whether I could make this green, but I can't. What about the seven then? The seven can't bump into the three, so it can now only get three horizontally, so it must take four vertically, not including itself. One, two, three, four, so it comes all the way down here. Can it get that one and then be seven vertically? I'm not sure.
Here is an obvious point: that must be gray, mustn't it? Because if that's not gray, this is an extension of this sort of yin-yang logic. If this is green, this gray connects to the edge somewhere. It could be there; it doesn't matter where it is, but you can see that it's going to create a wall that fences in some portion of the green cells in the grid, either this portion or this portion, wherever it connects. So you can't do that; that's got to be gray, and that preserves this as being a tendril. The same logic applies: this tendril is different from this tendril; otherwise, these greens will be shut in.
If this is gray, that's capping out this eight with a four horizontal. Two, four, five, six, so these two would be green. I keep thinking that my brain is starting to think of this in yin-yang terms, and that's not helpful because in yin-yang puzzles, you can't have 2x2s. Although this does have similar principles working in it, it's for completely different reasons, and I need to get away from that. I keep wanting to make this square green.
Where do you think we go now then? Somehow or other, this tendril, this tendril, this tendril, this tendril, and this tendril are going to meet somewhere around an i-pentomino in green. I wonder if it's there. No, it's not there, is it? The reason it's not there is weird, but let me just show you. It's not there because we worked out that the way the five tendrils operate around the i-pentomino is strictly in an on-off pattern. That would imply that this is on, this is off, and these are both meant to be different tendrils, and that's a green cell there, definitely not a tendril. So that's not possible. We can rule this square out as being a vertical i as the meeting point of the five tendrils. That sounds like a good film Peter Jackson should make.
If that's green, then this section—let's just think about that—if that's green, then all of those are green; otherwise, we introduce a new tendril. That's gray. This gray has to get out; that's not strictly true because the other tendrils could come to it, although I just feel that's so difficult to do. We might be at the point now where Nario's comment was something like more intuitively solvable than purely logically.
Solving puzzles often means finding the right connections and avoiding walls that split your progress.
That's not strictly true because the other tendrils could come to it, although I just feel that's so difficult to do. We might be at the point now where Nario comment—what was Nario comment? It was something like more intuitively solvable than purely logically.
I think the tendrils are going to have to meet in the middle of the puzzle, and it's going to be how we prove that if that's gray, then all of this tendril and this tendril get pushed together. I'm just going to look at that for a second. If that's gray, that's green, and this isn't a big enough tendril yet, so it has to grow, and this is now forced upwards. But now, how does that ever work? That comes out; that would have to come out. It's tricky. This is tricky.
What we really need to do here is to work out the location of just one tendril. Let's say I knew that this tendril was up here and exactly in this position. So let's just hypothesize that for a moment. We would then know that there was a tetromino that looked like this, and this was surrounded by green. But what we know that was far more important—in fact, I can actually see that this is an impossibility. Actually, I'm not sure it is impossible. I'm so sorry if this turns out to be correct; that's not my fault. I just thought it was impossible.
What I'm thinking is I now have to orthogonally connect this to the I pentomino. We know the pentomino joins everything up in green. Now, where are we putting that? We could put it horizontally there, but that doesn't work because of the on-off pattern. This should be a tendril and wouldn't be. We can't put it here vertically because this is taking too many sides of that I. The one place that I'm actually interested in is there because that's one tendril, that's the second tendril, so the other tendrils would have to meet in that pattern.
Actually, that's very hard to see, but you can see that's broken. That is broken because which tendril is this one? The only one it could be is this one, isn't it? But in being this one, it would touch this one, which is meant to be a different tendril, and that's impossible. Isn't that weird? Actually, that's very strange and incredibly complicated, but I've now proved—it's not actually going to help me—but I've proved that this isn't the limit of this tendril because if it was, I can't put the I in that I need to put in.
Right, so I've got to find something else to do here. I know that there's something gray in the bottom row. Yeah, so it must be gray. If that's green, I have to stop this being too big. Yeah, so that's gray. Ah, sorry, that's a very obvious point, but these could both be green if that's gray. Hang on, hang on. Isn't there a sort of—yeah, I've got to be very careful actually here. Right, here's a very obvious point that I hadn't appreciated until now, but now I do have to be a bit careful with checkerboards, don't I?
Creating a wall in the grid to separate sections is key to solving the puzzle.
In this process, however, I draw that tendril, I'm cutting the grid in half, effectively creating a wall. The way to think about it is that I'm creating a wall. In this case, that would be the wall. Although it might seem like a ludicrous wall, you can see that the greens on the left side of that wall cannot get to the greens on the right side. Once you have a diagonal connection and you're capped out on tendril, you must complete the connection orthogonally, and the same must be true there. This might affect this digit, which is now brilliant, isn't it? He's so brilliant, this man.
What is that? It cannot now be green; it could be green, but these can't both be green. We've only had a five count here, so we could get six there. We must take this, and in doing so, we actually complete the seven count, which has to be gray. The three count is completed, and this has to get out. This is going to be it.
I shouldn't have said that because it's broken again—not broken, but now, oh dear, how are we going to do this? I've got a problem. Let me try and articulate what I'm thinking about now. There's some area of this grid which is green where I put an I pentomino in, and it connects all the tendrils together. But look at this and look at this—how could they meet? Where do they meet?
What we've now learned is that the I is somewhere related to this column because we just can't get the regions to connect closer together than something like that due to the seven clue coming down the grid. Somehow or other, the I is going to be involved in cutting this seven, whether horizontally or vertically. The four is going to come out, but if that's true, and I think it is, doesn't this have to come out? Maybe it doesn't. That might be wrong.
If it just sits in its hole here, I don't know. This isn't that easy. What if it did that? No, because this is touching too many sides. Another interesting point about the I is that wherever we put it, it can only touch each tendril at one exact point, so we can't have it overlaying like that. Because now, I can't achieve the alternation I need.
If I were on a desert island now, I could solve this by just keeping looking at this column and trying out I pentominos in various geographies to see what worked. But there might be a better or more precise way of doing it. This five is interesting, isn't it? That could be green, or that could be green, or if both of these are gray, these three would be green, suggesting the I was going horizontally.
Solving complex puzzles requires patience and creativity; don't give up when it seems impossible!
If I make this gray, this green has to get out because that gray is not big enough. This three is forced. Now, I know that to connect this tetromino and this tetromino together, there's no way this can sit in its corner, so it's going to have to come out. This green has to come out. This has to get somewhere within reach of here, but it could be a horizontal eye, so we have to be careful. No, it can't look like that though, so I think it has to come out to at least here, and then that's going to have to come out.
There is no way it’s this shape because if it was this shape, the only cell of that tetromino that this could ever hit is that one, and then the alternation doesn't work. This should be gray, so I think that has to go out further. This has to be green. Now again, this is all so cluttered up. Somehow, I've got to have a tetromino that touches all of these tendrils and this one without these tendrils touching each other. How on Earth do you do that? I just don't think it's possible. There’s too much work for the green tetromino to do if you try and do this.
This has to connect via a single eye to a tetromino that joins not only this to this but also these. We can't do a vertical one like that. It works for these three on the right, but it never touches this one. If you had one that did that, it might be possible. Let’s just think about that. No, it’s too cluttered because these three ends don’t have enough space to fit into those four squares.
I’m unwilling to abandon that thought because this was all predicated on me sensing that this cell was very hard to make gray. By making it gray, I think I am now able to demonstrate that I can't connect the tendrils with anything because there is no eye I can draw in here. If we keep extending this, you definitely can't keep extending these because they can't touch; otherwise, they would be the same tendril, which is not right. We could do something like this, but now we need something that touches that one, which has now been fenced in, and something that touches these two as well and this one and this one with a single eye, where these aren’t allowed to meet one another.
Solving complex puzzles is all about recognizing patterns and connections.
I have now managed to achieve a three-tendril cut, but this can't exist in the pattern window because we're meant to alternate around the eye. The reason I was unwilling to abandon that thought is important. This square can't be gray, which caused all this kafuffle in the top right. If that's green, then there is not only a tendril that is short and sweet down here, but also that tendril has to have a tetromino in it, which now must be that shape. We must be able to connect an I tetromino to that in this grid such that all the other tetrominos, all the other tendrils, can touch it with the exact oscillation pattern that we're trying to achieve.
Now, where is that I? The I could be horizontal, but I don't think it can be horizontal. No, it can't be horizontal, so the I is vertical. Remember, we can't do something like that. There are many reasons you can't do that, such as that's a 2x2, but also we have to get the oscillation right along the tendril. If you did that, well, that's interesting; that actually might work, but that's not a proof, is it? What about that? No, that's interesting as well. Good G, this is so clever. This is such a clever puzzle. This is not the answer for the green tetromino.
Seeing that is a little tricky because what you have to recognize is that we're meant to oscillate around the boundary of this tetromino on-off, on-off. Cave versus tendril—those three are all the same; they're not on-off, on-off, are they? So that just is nonsense. We don't ever connect to this square. We don't connect to this, we don't connect to this, we don't connect to this. It has to be an orthogonal connection. I think that one might work, so let's try and rule out these two. I can definitely rule out this one. How does that one ever touch it? It can't, so that one's total. Actually, isn't that true for both of them? Yeah, it's that simple. You can't do those because this one can never touch that; it just can't touch it. So how can it be bridged by it? It can't. Either I've made a mistake, or that is the only tetromino you could possibly draw.
The interesting thing about this is if we go on-off, on-off around it, those would be on, these would be on, and this is on, so it does sort of look like it's going to work. Now, all these circles all have to be different tendrils. That one would have to be this one, which means this has to get out. This one—I'm not sure, but it's going to belong to that top tendril somehow. We might actually not be done yet. These all have to be kept apart because they're different tendrils.
This tendril attaches to this tendril; that must be true. The eight is done, and the five is done. Oh, this is gorgeous. Look, it's done. Everything's done down here. The eight's done. Two, three, four—I don't know how this five works or this one. Although this five can only take one vertically, so yeah, that's okay, isn't it? It could take both of those. Sorry, that's not a sensible thought.
Just solved one of the most mind-bending puzzles ever, felt impossible but nailed it with pure logic!
Sorry, okay, that's not a sensible thought. So, there is some way I'm meant to be able to detect. Remember that these can't touch diagonally. If that was gray, they would touch diagonally, and we've worked out that's an impossibility using our logic. So, this one closes like that. This three can't go all the way, can it? We've got to keep this one away from this one and this one, so it's going to form some sort of pattern up there, but I'm not certain I can see exactly what it is. Have I missed a clue then? Maybe that's what I've done. Oh, I know what it'll be. Oh, I've broken it. Oh no, no, this is beautiful. I've got it, I've got it.
Right, next question. Let's go back to the rules of the puzzle. We can't have the same tetromino shape touching. So, what tetromino shape is this? Well, it's going to at least here; it can't go there because that would be two eyes touching. So, it must turn up and in turning up, it turns this gray. Now, why is this interesting? This one cannot touch this one even diagonally, so that's gray, that's got to be green. The gray comes through there, the gray must go there. This three has to take that square now because it can only get one here. If that was green, then this tendril to connect has to be a vertical stripe, and that's going to create a vertical eye tetromino as the only option. So, that's got to be gray. Now, this five clue gets finished like that, and that five clue gets finished by that. This is now an L. This is an L. We don't know about this one yet, but this five is taking its whole count horizontally, so it's either getting this one or it's getting both of these.
I hope I haven't made a mistake because I do want this to be unique. This can't be gray because these two tendrils connect, and that's going to isolate this green, so that green does have to get through there. I sort of felt like that was true. That must be the same for that square, but I'm still not done. This has to connect; that's isolated. There we go. Now, this can't connect; that's the way the five connects. This has to get out and be a tendril, and this three isn't. That's it, we've done it, we've done it, and that must be right because there is no way that was so forced. You get an I, a vertical I, and five L's all connected to it. That is an absolutely mindbending puzzle, and I think I did it logically. I don't think I needed to resort to intuition. I had one bit where I had to think about this and the effect on the T over there, but I think everything else was okay. I mean, that was logical; it was just difficult.
That is a wonderful puzzle. It is so weird and different, and I absolutely loved it. That's one of my favorite puzzles that I've done this year. I know that probably sounds strange. By the way, that felt much harder than three stars. How long's that taken me? An hour and 10 minutes. I don't know, I did feel that was quite difficult. My goodness me, and the storm didn't turn off my computer. I must stop the video soon so that this video isn't lost because that is magnificent. I'm losing my voice. Let me know in the comments how you got on. I enjoy the comments, especially when they're kind, and we'll be back later with another addition of Cracking the Cryptic.