Author: Andrey Bogdanov
Divide the grid along the grid lines into regions. Each region must contain one orthogonaly connected area of white cells and one area of shaded cells. The pair of areas must be of the same shape and size. The areas may be rotated or mirrored. A number indicates how many cells of one color the region contains. A region may contain several numbers - in this case all numbers must be equal. Regions of the same size shouln't share an edge.
Grid control: To draw a cut click at the cell edge or move mouse along the line holding the button. You can also connect the centers of cells which belong to the same part with auxiliary line. In this case cut lines will be added automatically. More details about grid control are at the help page.