The digits 1 to 9 need to appear exactly once in each row/column/region. The regions need to be discovered! An arrow in a cell indicates that an uninterrupted sequence of exactly X cells in the direction of the arrow - beginning at the cell with the arrow - belong to the same region (X being the digit in the cell with the arrow). If there is another cell after the sequence of X cells in the direction of the arrow then this MUST belong to a different region. Not all arrows that would be possible with the shape of the regions are given.