Each row, column and irregular region must contain the digits 1 through 9
Within each region shade one tetromino of cells so that all shaded cells form one orthogonally connected area. Two tetrominoes of the same shape may not touch at a region border, counting rotations and reflections as the same. No 2x2 region may be entirely shaded
Small clues in each region give the sum of the digits that appear in the shaded cells
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