Shakashaka (also known as "Proof of Quilt") is a logic puzzle, invented by Nikoli. The task is to place one of the four isosceles right triangles in some white cells. Each triangle must occupy exactly half of its cell, but may be in one of four orientations. Every contiguous white region must be a rectangle or a square. A number in a black cell indicates how many triangles are adjacent to that cell by sides.
Cross+A can solve puzzles from