Shade exactly two cells in each 2×2 region, so that all shaded cells are connected, all unshaded cells are connected to the border of the grid and no 2×2 square (regardless of region borders) is completely shaded. Cells with numbers cannot be shaded. The numbers indicate over how many of the original 2×2 regions the respective group of unshaded cells extends. Unshaded groups may contain none, one or several numbers.
(Rules and example from WPC 2019 IB)
History of the puzzle
Invented by Bernhard Seckinger (Germany) in 2011. First appeared on LMD portal.