Shakashaka Explained

is a logic puzzle developed by publisher Nikoli.^[1]

Rules

Shakashaka is played on a rectangular grid of white and black squares. Some black cells may contain a number.

The objective of the puzzle is to place triangles in some of the white cells. There are four kinds of triangles which can be put in squares:

In the resulting grid,

• The white parts of the grid (uncovered by black triangles) must form a rectangle or a square.
• Black cells with a number must be orthogonally adjacent to the specified number of black triangles.^[2]

Computational complexity

It is NP-complete to decide whether a given Shakashaka puzzle has a solution.Furthermore, counting the number of solutions to a given Shakashaka puzzle is

1. P-complete

.

Notes and References

1. Web site: Puzzles of nikoli.com. Nikoli. 18 August 2021.
2. Web site: Rules of Shakashaka puzzle. Nikoli. 18 August 2021.