# Four Cells: An Introduction

This is a Four Cells puzzle, an area-dividing puzzle.

Rules of Four Cells:

• The grid is to be divided along the grid lines into areas containing exactly four cells.
• A number in a cell indicates how many of its four sides are segments of area boundaries. Note that this also includes the border of the grid.
• Line segments of area boundaries should not be left dangling. (See below for an example)
• An area may contain any multiple number cells (including none).

An example grid is shown below for greater clarity.

Example puzzle:

Solution to example puzzle:

The example below showcases dangling ends and is an incorrect solution to the puzzle.

Shown below is the actual puzzle to solve:

Good luck and have fun!

• (For what it's worth, I usually see it translated just as Four Cells, not the romanized Japanese version. Still looks like a neat puzzle though!)
– Deusovi
Commented Nov 15, 2020 at 11:37
• This is also known as Palisade in Simon Tatham's collection. Commented Nov 15, 2020 at 11:47
• Corrected Game ID 6x6n4:2b1i23a1m2b3 Commented Nov 15, 2020 at 12:04

Some basic deductions:

Next, look at

the 3 in the center. It must be a "dead end" of a region; if it goes up, then it must go left then, and we have a problem -- we can't make the fourth cell without running into the top 2's region!
So the 3 doesn't go up, and R2C3 is a dead end. Making sure to keep regions of size 4, we get to here:

Now let's look at possibilities for another clue:

specifically, the 1 on the right. It has to be the middle cell of a T tetromino; if the tetromino is oriented as ⊥, ⊤, or ⊢, it will cut off the upper right corner. So it must be a ⊣.

And finally,

if the 3 region goes down and connects to the two cells below it, the cell in R6C3 will be blocked off. So it must make an S tetromino instead, and this completes the puzzle!

• nooooo i just finished my write-up :'( heheheh
– oAlt
Commented Nov 15, 2020 at 12:08