# 15 Puzzle Home Thread



## molarmanful (Jun 5, 2015)

Hey guys,
I feel like 15 puzzle deserves a thread, even though it's not an official WCA event or twisty puzzle. I'm sure that a lot of people could benefit from the help and discussions in this thread. If this is in the wrong forum category, feel free to move it (if you're a moderator).

That being said, I'll outline some basic steps and tips for solving the 15 puzzle with LBL (if there are other methods, please describe them in a reply):
*1. First row (FR):*

```
1  2  3  4
x  x  x  x
x  x  x  x
x  x  x  x
```
Generally, you solve as 1-2>3-4, but if you want to get faster, try solving 3-4>1-2, 2-3>1-4, etc. depending on the situation. You can also solve 1,5,9,13 as a 'row.'
If possible, try to solve some of the second row pieces while finishing FR. For example:

```
2  x  3  4
x  x  x  x
1  x  x  x
5  x  x  x
----------
easily becomes
----------
1  2  3  4
5  x  x  x
x  x  x  x
x  x  x  x
```

*2. Second row (F2R):*

```
1  2  3  4
5  6  7  8
x  x  x  x
x  x  x  x
```
Solve the second row like you solved FR. However, you might want to try fringing, or solving a column while doing the second row. After fringing, you'll end up with this:

```
1   2  3  4
5   6  7  8
9   x  x  x
13  x  x  x
```

*3. L8P (or L6P if you fringed):*

```
1   2   3   4
5   6   7   8
9   10  11  12
13  14  15  0
```
Solve 9 and 13 first if you haven't already. Then proceed in one of two ways:
a. Solve 10-14>11-12-15. Conventional way, relatively easy L3P, okay chance of L3P skip.
b. Solve 11-12>10-14-15. Only use this if 11 and 12 are easy to place (i.e.: not flipped the wrong way). Super easy L3P, high chance of L3P skip.

You should also try out SlidySim, a nice 15 puzzle simulator that also contains slidy puzzles of other sizes.


----------



## cashis (Jun 5, 2015)

Cool guide. Thanks for making this thread.


----------



## 4Chan (Jun 5, 2015)

If 15 Puzzle starts gaining momentum, and quality speedsolvable 15 puzzles (or larger) become available, I will be so happy.

Please keep this up! 15 Puzzles are cool!


----------



## Berd (Jun 5, 2015)

I want a 15 puzzle with corner cutting!


----------



## TDM (Jun 5, 2015)

You should probably add ben's sim to the OP, since it's what most people use.

just recorded a 15 puzzle Ao5, uploading now, will post here when it's done
E:




6.432 Ao5, fading tiles.


----------



## qqwref (Jun 5, 2015)

I'm not sure this really needs a home thread other than ben's sim thread, but okay. Here's some useful solving info.

The standard speed method for smaller puzzles (like 15 puzzle) is fringe. Basically the puzzle gets divided up like this:

```
A A A A
A B B B
A B C C
A B C
```
You would solve the A pieces first, then the B pieces, then the C pieces. Inside each fringe, you can either do the row part and then the column part, or the column part and then the row part, or both at once (if you see a way to do that). More efficient solvers use a lot of clever tricks to solve fringes, which you can learn from watching Ben's videos or optimal-fringe solves.

On smaller puzzles you can get away with moving pieces over one or two at a time, but on medium size puzzles (such as 99 puzzle) you will want to move trains of a few pieces up or left at once - that is, you might find 3-4 pieces from the first fringe's row, then put them in a column and move them all up in a single looping motion. I usually try to find all the pieces 

On very big puzzles, fringe does work, but it becomes hard to tell the individual fringes apart, since there are so many colors. The best method seems to involve the grids color scheme, with a secondary scheme. Essentially the puzzle is grouped like this:

```
A A A B B B ...
A A A B B B ...
A A A B B B ...
C C C D D D ...
...
```
The squares A, B, C, D, ... can be any size but are commonly 1/4 or 1/5 of the main puzzle's size (so there will be 16 or 25 of them). Each of these squares has its own color, and then within a square, the secondary scheme lets you tell pieces apart so you can do a fringe or LBL solve. As for the actual method, you would bring all of the pieces of the first row of grids up to those locations, making a big rectangle; then, inside that row, you would bring all of the pieces of the first square left; then you would solve the first square. After that, you keep sorting squares until you finish the row, and then you do the entire thing again for the other rows of squares.

Also, people should learn mouse  Keyboard+macro > mouse > keyboard in terms of speed for big puzzles, but I and some others don't believe macros are fair comparison. You can do many moves per keystroke and get bursts of 100+ tps easily - it breaks the rule that an NxN puzzle should take (constant * N^3) inputs, and gives the grid method an artificial advantage due to working really nicely with spamming whole-row rotations (like L50 U R50 D ...).

Of course, ben and soup can provide more info


----------



## molarmanful (Jun 6, 2015)

Berd said:


> I want a 15 puzzle with corner cutting!


Here's a mod I did recently to a plastic 15 puzzle.
I basically sanded down the corners of each piece a tad bit ("Florian mod") and lubed the puzzle with RZ-50.
Really love how it turned out. This thing actually corner-cuts, and it also moves really quickly!


----------



## Berd (Jun 6, 2015)

molarmanful said:


> Here's a mod I did recently to a plastic 15 puzzle:
> https://www.speedsolving.com/forum/attachment.php?attachmentid=5187&stc=1
> I basically sanded down the corners of each piece a tad bit ("Florian mod") and lubed the puzzle with RZ-50.
> Really love how it turned out. This thing actually corner-cuts, and it also moves really quickly!


Very cool!


----------



## TDM (Jun 6, 2015)

molarmanful said:


> Here's a mod I did recently to a plastic 15 puzzle:
> https://www.speedsolving.com/forum/attachment.php?attachmentid=5187&stc=1


Image isn't working for me, and clicking the link in Berd's quote gives me an invalid attachment.


----------



## Berd (Jun 6, 2015)

TDM said:


> Image isn't working for me, and clicking the link in Berd's quote gives me an invalid attachment.


Yeah I just guessed by the description hahah.


----------



## molarmanful (Jun 6, 2015)

Edited the previous post. Check the link.


----------



## TDM (Jun 6, 2015)

molarmanful said:


> Edited the previous post. Check the link.


What's the bit of plastic sticking out of the 12 piece? Do all the pieces have that? That doesn't look like it's really doing much.


----------



## Berd (Jun 6, 2015)

TDM said:


> What's the bit of plastic sticking out of the 12 piece? Do all the pieces have that? That doesn't look like it's really doing much.


Torpedos hahah


----------



## cashis (Jun 6, 2015)

TDM said:


> What's the bit of plastic sticking out of the 12 piece? Do all the pieces have that? That doesn't look like it's really doing much.


I'm pretty sure that's what keeps the pieces from falling out...it interlocks with grooves on the other pieces


----------



## TDM (Jun 6, 2015)

Berd said:


> Torpedos hahah





cashis said:


> I'm pretty sure that's what keeps the pieces from falling out...it interlocks with grooves on the other pieces


Oh, of course.
But then... how did you get the pieces out to mod them?


----------



## cashis (Jun 6, 2015)

TDM said:


> Oh, of course.
> But then... how did you get the pieces out to mod them?



I guess just rip it out like a regular cube.


----------



## molarmanful (Jun 7, 2015)

TDM said:


> Oh, of course.
> But then... how did you get the pieces out to mod them?



Yeah, there are grooves to keep the pieces from falling out when overturned. I basically pried out the 12 and 15 pieces with a screwdriver (didn't break them, luckily) and everything was super-easy to disassemble after that. For reassembly, I broke off a bit of the 12 piece's "torpedo" so that the the torpedo could actually fit through the florian mod holes.


----------



## Hssandwich (Jun 7, 2015)

I modded my really bad 15 puzzle yesterday, I may have over modded though.


----------



## The Professor Cubers (Mar 21, 2018)

It seems as though the 15 puzzle hasn't been very popular over the past few years but I recently got into it myself. I think it would a cool event to have competitions for but I don't know how big the audience is for it. If anyone would be interested in trying to hold a competition please reply so we can make that happen.


----------



## Mech (Oct 5, 2019)

Hello, can anyone solve this? It's basically 15-puzzle but with numbers 1-8. The right one is how the left should look like in 62 moves


----------



## CLL Smooth (Oct 5, 2019)

Mech said:


> Hello, can anyone solve this? It's basically 15-puzzle but with numbers 1-8. The right one is how the left should look like in 62 moves


Yes. Is 62 moves important because I didn’t count? If the last three numbers don’t work out then you’ll need to swap two of the same number.


----------



## Ben Whitmore (Oct 5, 2019)

Mech said:


> Hello, can anyone solve this? It's basically 15-puzzle but with numbers 1-8. The right one is how the left should look like in 62 moves



It's possible in 28 moves: RDRURDDDLURULDLLDRULUURRDLUL


----------



## Iwannaganx (Oct 5, 2019)

Ben Whitmore said:


> It's possible in 28 moves: RDRURDDDLURULDLLDRULUURRDLUL


How does this notation work


----------



## Ben Whitmore (Oct 5, 2019)

Iwannaganx said:


> How does this notation work



Move one piece right, then one piece down, then one piece right, one piece up, one piece right, three pieces down, etc.


----------



## Mech (Oct 5, 2019)

CLL Smooth said:


> Yes. Is 62 moves important because I didn’t count? If the last three numbers don’t work out then you’ll need to swap two of the same number.


 Yes the count of moves is essential.



Ben Whitmore said:


> It's possible in 28 moves: RDRURDDDLURULDLLDRULUURRDLUL


Great one, it worked. Thanks for helping


----------



## ImmolatedMarmoset (Dec 26, 2019)

Anyone got a good alg for cases like 

1 2 3 4
5 6 8 7
x x x x 
x x x x

or 

1 2 3 4
5 6 7 8
13 x x x
9 x. x. x


----------



## Natanael (Dec 26, 2019)

For the first case I put the empty tile below the seven and do: D R U L U R D D L U R U L D D R U


----------



## Natanael (Dec 26, 2019)

I just found a better way: empty tile below 8 and do: R D L U L D RR U LL D R U, these are some I found myself, there are probably better ones.


----------



## Etotheipi (Jan 19, 2020)

What methods do you guys use for 15 puzzle? My method is to solve 1 2 3 4 5 9 and 13, to reduce it to a 3x3 grid, then solve 6 7 8 10 and 14, then just cycle the last 3 pieces. I came up with this on my own, so its probably quite bad, but methods do you people use?


----------



## Ben Whitmore (Jan 19, 2020)

That's the fringe method, which is the best method. There aren't really any other methods (on small puzzles, anyway) other than solving row by row. But since square puzzles usually take fewer moves than long rectangular puzzles with the same number of tiles, fringe is usually a bit more efficient than row by row.


----------



## Etotheipi (Jan 19, 2020)

Ben Whitmore said:


> That's the fringe method, which is the best method. There aren't really any other methods (on small puzzles, anyway) other than solving row by row. But since square puzzles usually take fewer moves than long rectangular puzzles with the same number of tiles, fringe is usually a bit more efficient than row by row.


Ok then. =P Thanks.


----------



## ProStar (Jan 20, 2020)

Best 15 puzzle?


----------



## GAN 356 X (Jan 20, 2020)

ProStar said:


> Best 15 puzzle?


Qiyi klotski haven't tried it but it looks good


----------



## CodingCuber (Apr 1, 2020)

So I got a 15 puzzle and I made up this method to solve it. Someone else probably already created it before me but yeah.

First, you do the top layer and the numbers along the vertical line on the left.

Now, you have reduced the rest to a 3x3 grid and you just solve the rest.


----------



## ImmolatedMarmoset (Apr 1, 2020)

CodingCuber said:


> So I got a 15 puzzle and I made up this method to solve it. Someone else probably already created it before me but yeah.
> 
> First, you do the top layer and the numbers along the vertical line on the left.
> View attachment 11604
> ...


Yup, that’s called fringe. Nice job discovering that out.


----------



## ProStar (Apr 1, 2020)

I'm starting to use fringing, and I keep getting stuck at the 3x3 grid and it will take me like 20 seconds


----------



## DerpBoiMoon (Apr 25, 2020)

So I'm averaging sub 90 on it, using a virtual puzzle. My real life one is so bad. Should I get the qiyi one? And any tips to be sub 1?


----------



## Kaneki Uchiha (Apr 25, 2020)

practice a lot 




i have not done it ever dont listen to me


----------



## DerpBoiMoon (Apr 25, 2020)

New pb 51.37

Shoot, just got a 37.3!



DerpBoiMoon said:


> My real life one is so bad. Should I get the qiyi one?


Yes, you should.

I'm pretty mediocre at 15puzl (used to average 17 on slidysim) but generally you should know immediately which pieces go where (i.e. you should know 1,2,3,4 are the top row and 1,5,9,13 are the left column). Do a hundred solves and it should become second nature. Also, don't stare at the pieces you're solving; look at the pieces you need to solve next.

As far as virtual 15 puzzle goes, keyboard controls are probably easier to get fast at than mouse/touch controls.


----------



## ProStar (Apr 25, 2020)

Definitely get the Qiyi one. I'm averaging around 25 and am switching to fringing. Right now it's just about solving, I got down to 25 with around 100 solves


----------



## dphdmn (Apr 27, 2020)

You can get sub 20 really fast, just solve it and try to remember what r u doing


----------



## brododragon (Apr 27, 2020)

I can't find any mobile sims that don't scroll when you do moves. Anybody know a good one?


----------



## DerpBoiMoon (Apr 27, 2020)

15 puzzle, from the play store


----------



## brododragon (Apr 27, 2020)

DerpBoiMoon said:


> 15 puzzle, from the play store


Anything online?


----------



## DerpBoiMoon (Apr 27, 2020)

__





Fifteen Puzzle Game


Fifteen Puzzle game (15 puzzle-game): move tiles in grid to order them from 1 to 15!




lorecioni.github.io





This is online, though you just press the tile. So you won't need to scroll.


----------



## brododragon (Apr 27, 2020)

Ayy solved it totally didn't just build the first 3 layers and mess around until I solved it.


----------



## dphdmn (Apr 27, 2020)

brododragon said:


> I can't find any mobile sims that don't scroll when you do moves. Anybody know a good one?



idk what scroll means but
best app atm https://play.google.com/store/apps/details?id=com.italankin.fifteen
use hover control


----------



## dphdmn (Apr 27, 2020)

DerpBoiMoon said:


> __
> 
> 
> 
> ...


this thing is bad. illegal scrambles

good (not great) web mobile thing https://fifteen-collect.github.io/frontend-js/


----------



## DerpBoiMoon (Apr 27, 2020)

dphdmn said:


> idk what scroll means but
> best app atm https://play.google.com/store/apps/details?id=com.italankin.fifteen
> use hover control


That's what I said


----------



## BenChristman1 (May 1, 2020)

I got 6:57 on 7x7 sliding puzzle:


----------

