Logic Masters Deutschland e.V.

Place a digit from 1-9 once each in every row, column, and cage.

If and only if adjacent digits do not sum to a prime number, shade the boundary between them. Shaded boundaries must divide the grid into exactly 2 regions. There may be shaded boundaries that lie within a region without fully dividing it.

A digit in a cell with one or more arrows indicates the total number of shaded boundaries in the directions of all arrows combined.

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