Example puzzle
This is an example puzzle. You can solve it the same way as you would solve competition puzzle, but result never stored. You can reveal an answer for the puzzle by clicking "Show answer" link.
Black and white
Author: Andrey Bogdanov
Divide the grid into rectangles. Each rectangle must contain exctly two circles - one black and one white.
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 rectangle with auxiliary line. More details about grid control are at the help page.