Heyawake is one of the Nikoli original puzzle.
"Heya" means "room", "wake " means " divide".
So, Heyawake means "divide a room".
You may feel rules are little bit complicated but once you get familiar with it, it's very interesting.
1) Rectangles divided by bold lines is called "Room".
2) Shade some of the cells black in the grid.
3) Number indicates No of black cells present in that room.
4) Black cells must not be vertically or horizontally adjacent.
5) Remaining white cells should be connected to each other
via vertically or horizontally.
6) However, any single horizontal or vertical line of white cells
cannot traverse more than two thick line.