Doppelblock ("Double Block") consists of a square grid. The goal is to blacken two cells in each row and each column. The remaining white cells must be filled with the digits from 1 to N-2, where N is the size of the puzzle's side. Each digit appears once in every row and column. Numbers outside the grid show the sums of the digits between two black cells in corresponding row or column.
Cross+A can solve puzzles from