Rules: (as taken from the WPC instructions)
Fill each empty cell with either a black circle or a white circle. All white circles should form an interconnected area and similarly all black circles should form an interconnected area. There cannot exist any 2x2 cell region consisting of same colour circles anywhere in the grid. There is the same number of black and white circles in the grid.
#218 Yin Yang – rated mediumAll puzzles © Tom Collyer 2009-12.