Logic Masters Deutschland e.V.

Place a number into some cells so that all cells with numbers form one orthogonally connected area and no 2x2 region is entirely numbered. Each region must contain at least one numbered cell, and every number in the region must be equal to how many numbered cells the region contains. A clue in a region represents how many numbered cells are in the region. Two cells containing the same number may not share a region border. There may not exist a run of more than three consecutive numbered or unnumbered cells horizontally or vertically anywhere in the grid.