How to Solve a Slitherlink Puzzle

This is a video about solving slitherlink puzzles. This one comes from Grandmaster Puzzles. It was original designed by Grant Fikes!
Link to puzzle: www.gmpuzzles....
Other Slitherlink puzzles by Grandmaster Puzzles: www.gmpuzzles....
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Intro song: Tekvision - Mycoplasma
Intro template: /SDJGRedstoneDJ
FLEB is a family friendly channel devoted to teaching people about the puzzle world, solving techniques, and all the different ways to have fun with puzzles!

[@acorn072681]

Awesome! More of these puzzle solving videos please. Love them all. Great job.

[@hal013]

I enjoy watching these paper and pencil puzzles as much as the physical ones! There's so much logic involved

[@auedpo]

I have really been enjoying seeing all of the paper logic puzzles! Thank you for sharing :)

[@FLEBpuzzles]

Thanks Austin! I hope to make this into a weekly series on Monday! I think paper puzzles are a great day to start the day, if not the week. :p

[@michielhorikx9863]

I have also been enjoying the paper puzzles a lot. Thank you very much for the great content!

[@mimisaiko]

Never knew this kind of puzzle! I love it I also love Dungeons & Diagrams in Last Call BBS.

[@sierra3159]

this is one of the first puzzles i’ve seen (i haven’t seen many) that i actually want to try asap :)

[@FLEBpuzzles]

Go for it!

[@lagduck2209]

Wow that's some cool puzzle, simple in rules and quite logical in solving, and not obvious at.

[@CSmyth-]

Slitherlink is my favourite! I solve at least two every day. Once you get good at them, they become so automatic and it only comes down to how fast you can draw the lines lol. Generally only takes me 45 seconds to a minute on average. Honestly FLEB, thank you for covering this! :D

[@FLEBpuzzles]

I'm glad you enjoyed it! If you're good at Slitherlink, have you seen Kwon Tom Loop? There are a lot of very hard puzzles there. kwontomloop.com/

[@CSmyth-]

FLEB That is awesome. Thank you so much!

[@wwerules01]

I am really enjoying this series of puzzles. What looks very hard at first, you break down into easier bits and this makes the puzzle more straight forward to complete, but I know for a fact if I tried to do these puzzles by myself I would get lost within 10 minutes lol.

[@FLEBpuzzles]

You should give it a try!

[@pijiroe]

Hey Fleb! Thank you for introducing logic puzzles to me, they are all really fun and challenging. Recently I discovered picross, which is also really great fun. I haven't done it in paper form yet but you should do nonogram puzzles next. All the best!

[@FLEBpuzzles]

Thank you! I'm sure nonograms will appear here at SOME point! :p

[@-JiminP-]

Ah, this is my favorite type of puzzle in the Simon Tatham's Portable Puzzle Collection (it's named 'loopy' there). I like how creative clue patterns can be, and finally drawing a closed loop after backtracking without crossing out any line segments is really satisfying. There are a few more clue patterns I use: * If you draw any closed loop, then there should be even numbers of crossings. * If two 3 squares share a side, then that side and two other sides parallel to it should be connected, and two segments next to the shared side (not a side of either of two 3 squares) should be crossed out. - This is similar to what was shown in the video for two 3 squares share a vertex. * If a 2 square or a 3 square is in a corner, then two line segements can be drawn for each case. (What are they?) * Every vertex is shared by exactly two line segments. This seemingly trivial fact have a lot of *very* powerful consequences, which I'll skip here.

[@rmsgrey]

That last fact isn't always true - in fact, it's not true for the example puzzle. What's true is that each vertex has either 2 or 0 line segments. There's another technique I occasionally use - and that's to label inside and outside squares - if two squares are separated by a line, they must be one inside and one outside, and vice versa - an inside adjacent to an outside must be separated by a line. I believe for a straight Slitherlink, anything it makes clear can also be solved by finding an appropriate closed loop and forcing an even number of crossings, but there are variants where you get some in/out information, and even in a straight Slitherlink, I sometimes find it easier to keep track of in/out rather than trying to find a suitable loop path.

[@-JiminP-]

Ah, thanks for pointing out my mistake. Yes, each vertex is shared by *zero* or *two* line segments.

[@stevethecatcouch6532]

There are also slitherlink puzzles on grids other than square, for example slitherlink on a hexagonal grid. Some of the clue combinations work similarly on other grids. For example 5's on a hex grid act like 3's on the square grid.

[@FLEBpuzzles]

Right! There are lots of variations! (I personally like variations more than classic puzzles, but ymmv)

[@bg6b7bft]

I love the "Great Dodecagonal" variant on Simon Tatham's portable puzzle page.

[@arturovial1631]

I like the one with rhombii, and the Penrose tesselations are beautiful and fun to solve too!

[@katarzynaw4664]

I was waiting for this one! Now I feel I need to try some for myself ;D

[@leahmccool4101]

Puzzles like this are my favorite but I cannot figure out how to solve these. I’ve rewatched this video so many times while trying to solve super easy puzzles and still can’t figure out how you know which way to go when it seems like there’s more than one option

[@wwerules01]

Miss these puzzles be @FLEB

[@rosebuster]

Hey! I actually solved this exact type of puzzles in the past included in a scientific magazine. They had this puzzle zone with many cool things like this one. It wasn't too hard, but always fun! That's also where I completed a sudoku for the first time, way before it exploded in popularity. Back then I felt like the cool kid being able to solve it while nobody knew it existed. They didn't even call it sudoku back then.

[@Nostson]

You seem to be doing a lot of path puzzles lately, have you checked out a videogame called The Witness? It uses a modified version of this particular puzzle very well.

[@FLEBpuzzles]

Yeah, I LOVED that game. Just devoured it.

[@Ramzuiv]

I'd like to see more of these pen-and-paper puzzle videos

[@bb5bucks]

I’ve been doing these online since seeing this. I’ve shared them with my friends, too. They seem to take a guess and check approach; that doesn’t work too well.

[@donnypassary5798]

Yes! Another one of my favourites!

[@FLEBpuzzles]

Do you solve a lot of logic puzzles?

[@donnypassary5798]

I love these kinds of numbers and logic puzzles since I was a kid. Back then before internet was even a thing, there's a puzzle magazine in my country focused on these kinds of puzzle (slitherlink, sudoku, masyu, battleship, etc) and I like to solve it ever since. I couldn't tell how happy I am to see you actually solve these puzzles by walking through the logical steps, some of the ideas are really new to me (especially on star battles). Hope you will do this with some variants of the well-known puzzle too!

[@FLEBpuzzles]

Nice! I hope the videos introduce you to some new types! I've always found them fun as well.

[@ehsan_kia]

People who enjoy these kind of puzzles should check out "Simon Tatham's Portable Puzzle Collection". It's a collection with dozens of puzzles including this and other like it. It's available on many platforms including Android/iOS. It has a fantastic UI, allows you to generate an infinite number of puzzles and it's entirely free.

[@TheBigA]

Ehsan Kia Thanks so much. I just got that app and it’s great and there’s unlimited puzzles and you don’t need WiFi to create them!

[@Dumb-bejad007]

but i think Rusty Lake games r better 0_0

[@nonduduzosamkelisiwe7320]

Very interesting!!! This is a good tutorial

[@hawk0485]

I would thoroughly enjoy watching you play Portal 2 and seeing your thought process as you solve the puzzles. Would you consider doing that? Perhaps on twitch if not on your youtube channel...

[@FLEBpuzzles]

Definitely! I'm hoping to start a stream of some sort soon. Stay tuned...

[@DemonChildCC]

Seems like an interesting one..

[@FLEBpuzzles]

I hope you enjoy it!

[@DemonChildCC]

FLEB I hope so too.. this channel has opened up a whole new world of puzzles I've never even heard of and wanna try..

[@gothemcloud]

alot like minsweeper, i could get into this

[@bobbyberetta4206]

Very well explained

[@pattycakesxd9672]

Nice video! It’s just like the triangle puzzles in The Witness, except the slitherlink puzzles are harder!

[@FLEBpuzzles]

When I came across those in "The Witness", I was like "Oh, that seems familiar!"

[@MorseAmalgam]

I'm curious - are there any rules or particular things that need to be considered if you want to MAKE one of these puzzles? It seems like it would be fairly straightforward, but at the same time I could see it being easy to run into the pitfall of making a puzzle with a solution that isn't inferred from the hints given.

[@FLEBpuzzles]

I'm hoping to do some more videos on these types of topics soon! Essentially, you need to make sure the puzzle is unique. You might start out with an idea for an overall way the puzzle solves or a set of cool clues, and then add clues in to make the rest of it unique. You often have to undo previous work, and it's very non-deterministic and fluid. At least, that's how it feels to me. The best way to see that for yourself is to try to construct one! Start with a small grid, and see if you can make a puzzle that's unique. Then try to make the clues symmetric. Try to add in your own ideas for new clue combinations. It's a lot of fun!

[@MorseAmalgam]

Thank you for your reply! I've enjoyed seeing all the puzzles you share. I look forward to videos on the design process should you decide to go that route! I was mostly curious in this instance if there are rules to making slitherlink puzzle permutations. It seemed like it could be a fun project to try to make a generator for them, but I wasn't sure if there were particular elements that needed to be considered when figuring out, say, how many numbered tiles to put in.

[@FLEBpuzzles]

That's an interesting question. I think there's probably a minimum clue count, but I don't know what it is. I don't know very much about procedural puzzle generation, unfortunately.

[@mlfan5986]

For fun, I started working on a star battle puzzle, because they stood out to me as having very elegant solutions. It's really fun, but surprisingly hard to make sure that A: there's only one solution, and B: there's a solution at all! I'd love to see how you would go about making some type of similar puzzle. I agree with the uniqueness thing, oftentimes, with a star battle puzzle, I start with one unique 'setpiece' moment and work from there.

[@AbiGail-ok7fc]

FLEB The minimum clue count for any sized board is one: a single 4, which leads to a tiny four edge loop. If you want to exclude a 4 as a clue, you can force a six edge loop of two 3s next to each other, surrounded by a ring of 0s (on distance two of the 3s away). Again, that works for any sized board (assuming it's large enough to contain the pattern of clues).

[@aquawoelfly]

My solveing stratagy... Zeros obviously solve themselves. Then i look for 0+3 and 3+3. Next i draw lines getting out of these areas. Any corners/edges (such as the 1+2 and a 0 neerby the top left corner on the example grid. 1+2 the line either goes between the 1 and 2 or around the combination. In this case the 0 prevents it from go8ng around so it goes between. After i have some obvious connections i start drawing more lines away from the segments that have been drawn. Next i look at numbers neer the ends of my drawn lines to see how the line can continue. If i run out of numbers very close to the drawn line segments i look for othe number combinations that have one or very few options and narrow that down (repeat this step) Connect any line segments not currently connected

[@arcan_ky5883]

thanks boddie, it will be a helpful on the exam :))

[@thecaneater]

Once you explained the rules, I copied it into Paint. I wanted to see how well I could do on my own. ... And I managed to complete it fairly quickly. Thanks for sharing.

[@FLEBpuzzles]

Nicely done!

[@etopowertwon]

Nice. It was fun to printscreen the puzzle and solve it in gimp. I didn't immediately notice corner trick in 3+3 pair at 4:05 (I think it was the hardest part in the puzzle, took me 20 minutes probably) but instead found that if middle is not filled, then the pair will form the closed loop : ⊏⊐. I've found that marking spaces that can't be used for segments with different color rather than just `x` helps a lot. (Same in masyu: with drawing a wall instead of `x`)

[@rmsgrey]

Yeah, with 3s next to each other, you have to get an S loop through them, so you can fill in |3|3| and block above and below the middle line (or equivalent rotated 90 degrees if they're vertically adjacent); diagonally adjacent 3s have to have lines on the sides away from the other 3, but not the neighbors. There's also corner rules for 3s and 2s - for a 3, the gap can't be in either of the corner edges because that would leave a loose end in the corner, so you can fill in those two edges. The corner rule for 2s is more complicated to work out and doesn't automatically let you write anything in unless you have some additional constraints nearby...

[@globe623]

Love ur vids!!

[@FLEBpuzzles]

Thank you akshin!

[@AgentArcadia]

Fleb, have you heard of a game called The Witness? It houses a lot of these paper-based logic puzzles you love (as do I), and it's probably worth sinking a couple hundred hours into to complete

[@FLEBpuzzles]

I loved playing the witness!

[@monta1994]

Good day and Merry Christmas Fleb! Me and my friends are going to conduct a puzzle hunt party before new years eve. What place would you recommend to give me ideas for puzzles? Your videos are great! However I think they're too difficult for me to give them these kind of puzzles. I hope you see this! Happy holidays

[@jacksainthill8974]

There are many (open ended versions) of these in Jonathan Blow's _The Witness._

[@Iscannon]

FLEB COME BAAAAACK

[@PhilipBlignaut]

Our local newspaper used to have these on their jokes and puzzle page, but replaced it with a second sudoku puzzle... :-(

[@FLEBpuzzles]

That's so sad!

[@Alvin_Vivian]

I actually enjoy Slitherlink more than Sudoku.

[@sinom]

I really want that pencil

[@salimabdi1366]

keep up the good work :)

[@FLEBpuzzles]

Thanks Salim! Good to see you, hope you're doing well!

[@mazerescue]

This reminds me of minesweeper, using the numbers to figure out what can go where.

[@MrVankog]

Had fun with all kind of Slitherlink variations over the years. For Android, I recommend *"Slitherlink" by Ejelta LLC.*

[@eitanlim1926]

This is how a Slitherlink puzzle works: 0: you *cannot connect* dots around it. 1: *you can only connect* dots to 1 dot around it. 2: *you can only connect* (make sure you choose the right two dots surrounding it) to two dots around it. 3: *you can only connect* (again make sure you choose the right three dots surrounding it) to three dots around it.

[@LazyCrazyCat2]

How much time do you need to solve a hard puzzle?

[@avisian8063]

FLEB hae you played The Witness?

[@PencilCase6B]

Joining the question. It's a must-play for him.

[@FLEBpuzzles]

I have! It's great! At some point here I'll make a "Top 10" video of my favorite puzzle games, and it'll be on it!

[@mr.nerd3.142]

This is getting into MINESWEEPER territory.

[@CannedKiwiSKC]

Reminds me a lot of Picross puzzles

[@quatreiquorizawa9885]

Thank you for changing the pencil from your similar puzzle video. no irritating noise anymore :)

[@CSmyth-]

Quatrei Quorizawa One person's irritating noise is another's ASMR :P

[@FLEBpuzzles]

Well now I don't know what to think!

[@quatreiquorizawa9885]

Just think of more puzzles to share to us :)

[@thecaneater]

Next, he needs to get a proper eraser. But at least this one is better than those pick stiff pink ones he's used before.

[@rosebuster]

But... but.. I enjoy listening to the scratchy noise of a pencil on paper!

[@rmsgrey]

For loop puzzles, the ultimate I've encountered (so far) is the Area 51 puzzles invented (so far as I can tell) by David Millar at thegriddle.net. His are at thegriddle.net/tags/areafiftyone There's an online version at krazydad.com/tablet/area51 The puzzle uses a mix of Slitherlink, Masyu, Corral, and In/Out clues. Mr Millar has also come up with various variations on the theme - like requiring the loop to pass through every vertex, or having some additional restrictions on some cells.

[@juliawhitmore3991]

Anyone got any good recommendations for apps for games like this one, Masyu, Starbattle, etc? I downloaded a Starbattle app recently that I've been working my way through, but I'll solve them all eventually and then what will I do with my time?? Rewatch FLEB videos I guess

[@Dumb-bejad007]

hai Fleb, have u ever played Rusy Lake games? th puzzle r so fun :3 u can find it in appstore

[@dalecai2455]

Anyone else getting Minesweeper vibes from this

[@nikolaipenev8349]

very much so

[@D-Brow]

why do you take your comfort socks of those perfect pencils? I buy the same ones and love them just how they are 😊

[@nurulhanim6126]

'Hey there! My name is FLEB' WHAT? DATS YOUR CHANNEL NAME'S🤪

[@woopersquirtle1422]

KZbin says that your category is film and animation.

[@syossee]

Have you ever played The witness video game?

[@FLEBpuzzles]

Yep! Loved it!

[@TrashSquid]

One of the first

[@MasterMindmars]

This game is programmable in a computer and is very addictive. Could be improved with more things to do. Even could be 3d. Thank you

[@bt9246]

i like ur vid

[@FLEBpuzzles]

Thx

[@skippyjones180]

Is your name actually fleb

[@DailyGamage]

Fleb do a puzzle giveaway

[@umakameswarimadhira1742]

👍🏽

[@repinswatson6452]

Reminds me of minesweeper sorta.

[@haoncs]

im really fucking stoned rn

[@caerys]

this is hype

[@mehmetkayhan1829]

Tekyu

[@glmathgrant]

Who's this Grant Fikes guy? His puzzle is terrible. It has too many numbers in it. I'm allergic to numbers.

[@FLEBpuzzles]

lol! Like I said, ask cryptically and ye shall receive.

[@rosebuster]

A puzzling furry! Aaaaaa! They exist! I want to high five you!

[@devjock]

Awesome puzzles Grant! If this gets picked up by some newspapers/magazines for "monthly prize puzzles" or something of the likes, it might become the next Sudoku craze. Loving these puzzles!

[@glmathgrant]

*hugs Maks!*

[@rosebuster]

Grant Fikes *hugs back* :)

[@JudeisJinxed]

Fortnite lmao

[@dap7650]

jt??

[@reghudevapriya5272]

kzbin.info/door/8DapcRD9coWWKU4rmHZhAQ

[@toshikobiko]

9th comment

[@toshikobiko]

I

[@warcatbattalion]

more physical puzzle and less paper pls

[@ryderpham5464]

Personally, I like the paper puzzle variety because they're cheap and accessible

[@thecaneater]

Check out Mr. Puzzle. Seems to be his specialty.