Each given pivot point in the puzzle forms the centre of a shape with rotational symmetry - the shape is the same when rotated 180 degrees. None of these shapes overlap, and all squares are in exactly one shape.
These puzzles can have arbitrary regions, but usually they reveal a hidden picture by shading in areas to match their given pivot colours. In a black and white puzzle these would be either black or white, as shown in examples below.
Like most logical puzzles, the difficulty can vary from easy to very hard, and the shapes found in the final solution can vary from simple to surprisingly complex!
