Divide the grid (except the shaded cells) into regions of given sizes, so that each region contains exactly one black circle and one white circle. No 2×2 square can be located completely within one region. The shaded cells are not part of any region.
(Rules and example from WPC 2019 IB)
History of the puzzle
Invented by Roland Voigt (Germany) in 2013. First appeared on Hausigel Contest Series.