Friday Puzzles #182

Once again dearest reader, I find myself in something of a rush.  This week's puzzle is going to be really quite easy (alas for uniqueness issues - again!!) if you know the tricks, or else quite a bit harder if you don't.  I'm not sure how well known these tricks are beyond the hardened puzzling community, so I'm going to hedge my bets and call this a medium.  Enjoy!

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 medium

All puzzles © Tom Collyer 2009-12.