Author: Andrey Bogdanov
Divide the diagram along the grid lines into regions of equal sizes. Each region must contain exactly one cell with a clue. The number indicates the number of neighbors of this region. Two regions are neighbors if they share an edge. If clue is a question mark then the number of neighbors is unknown.
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 cells which belong to the same area with auxiliary line. More details about grid control are at the help page.