1. Line must be straight.
  2. Line must be continuous.
  3. Line must not intersect itself.
  4. Line is allowed to take 45 degree turns to itself, for example:

angle rule

The dots:


  • $\begingroup$ Does it matter how wide the line is? $\endgroup$
    – Stomf
    Sep 1, 2023 at 11:52
  • $\begingroup$ @Stomf - the line's width is intended to be not bigger than the width of a dot and not so narrow that it is not visible. But since rules do not prohibit the grid-wide line anything goes :D Not going to change the rules after the puzzle has been solved. $\endgroup$ Sep 1, 2023 at 15:57

2 Answers 2


It is not written that the lines can or cannot leave the square...

What about this?

enter image description here

  • $\begingroup$ That is one of the correct solutions, yes. $\endgroup$ Aug 30, 2023 at 12:56

Now that the devil is out of the box, let's see what is the minimum of lines that can cover all dots.

The minimum I can do is

13 lines.

And here is how it can be done.

But before looking at the solution, have a try!

enter image description here

  • $\begingroup$ Very interesting, may I ask what did you use to find the minimum of lines? $\endgroup$ Sep 1, 2023 at 18:24
  • 1
    $\begingroup$ Pencil and paper. ... and eraser. $\endgroup$
    – Florian F
    Sep 1, 2023 at 18:33

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