Fill the cells with the digits 1 to 8 such that each digit appears exactly once in every row, column and region. A region is a collection of eight orthogonally connected cells. Determining the shape of the regions is part of the puzzle. Each region has exactly one clue which is a small number in the upper left corner of some cell in that region (not necessarily the top left cell). Shade some cells such that: a) no orthogonally neighboring cells are shaded across a region boundary; b) all shaded cells within a region are orthogonally connected; an c) the digits in all shaded cells within a region sum to the region's clue. If all of the shaded groups were to fall straight down without changing shape, they must completely fill the bottom half of the grid.