Contents of Key to solution for Slither Link

Key to solution for Slither Link

Rule details


  1. Connect dots with vertical/holizontal line and make one loop.
  2. Numbers define how many lines can be drawn around it.
  3. Lines cannot be crossed or branch off.
You are free to draw or not to draw lines around places without numbers. You are making one big loop, so dots on the loop always connect two lines.

Now I start detailed explanation with simple example.


< Example >

I will use 5x5-size question as a simple example.

You are free to draw or not to draw lines around box without numbers.


< Step 1 >

It is helpful to mark "x" at where you can't draw lines.

First, note that no lines can be drawn around "0".


< Step 2 >

Next let's take a look at "3" next to 0. 3 means there is one side without line around it. So when 0 and 3 are next to each other, you can't draw line between them and obviously the other 3 sides to draw line will be decided.

< Step 3 >

To make one big loop, lines around "3" must be connected with upper and lower dots respectively. Because you cannot end the loop here.

< Step 4 >

A corner dot is special. If the loop goes throuth it, you must draw two lines connecting the corner dot. On the other hand, if the loop doesn't go throuth it, those two sides which are connected by the corner dot must not have lines.

Therefore, when there is "1" at a corner, you can mark "x" on the two sides of the corner.

On the contrary, when there is "3" at the corner box, lines must be drawn on the two sides.


< Step 4 >

Now, do you see you cannot draw lines at "a" and "b" ? The reason is you cannot extend line beyond them. So, for those two "1s" at upper and lower left corners there are only one sides left to draw lines and the loop must take a turn.

< Step 5 >

By the way, when two 3s are adjacent vertically or holizontally, you can draw lines and mark "x" like this. I won't explain this further so please find the reason yourself if you want to know it.

< Step 6 >

Let's take a look at "c" and "d" around number 1. When you look at the upper left corner of this "1" (a corner formed by "c" and "d"), you will notice the sides beyond that point are marked with "x" because of "0". This makes the situation same as "1" of <Step 4>, so "c" and "d" will be marked with "x".

Now three sides are marked with "x" and obviously the remaining side will have a line. After you draw a line there, the question will be look like left figure.


< Step 7 >

Next take a look at "3" at the middle of the top row. The end of loop at dot "e" must go around "3". There are two possibilities. Those two sides must have lines in both cases. You should see it by now.

< Step 8 >

Then look at "2" placed at lower right of the "3". Top and left sides of the "2" must be marked with "x" and it decides where you must draw lines around "2". In the same manner, you will see where to draw line for the "2" at lower right of this "2".

< Step 9 >

The right line around "2" at rightmost column extends above. The line connects to other line which goes through upper right corner and runs around "3". It should extend below to connect with lower line.

< Step 10 >

Now you don't need more explanation to finish up. It is clear where to draw lines and finally one big loop completes.


Isn't it easy? Usually there is no detailed explanation like this. Find or learn "rules" and use it. Your skill will be raised and this puzzle will be easy for you.


Contents of Key to solution for Slither Link