Irasuto rule
Irasuto grid contains white and black cells with numbers. The goal is to blacken some cells of a grid according to the following rules:
A number in a white cell represents the number of empty white cells that can be seen from that cell.
A number in a black cell represents the number of empty black cells that can be seen from that cell.
A number in a white cell represents the number of empty white cells that can be seen from that cell.
A number in a black cell represents the number of empty black cells that can be seen from that cell.