Place 1-6 in each row, column and marked region. One cell in each row, column and box is a doubler. The value of this cell counts as double its digit for the other rules. Each digit appears once in the set of doublers. Digits along an arrow sum to the value in that arrow's circle. Digits in a black circle must not appear AS VALUES in the surrounding four cells. For example, a black circle containing a 4 excludes both a regular 4 and a doubled 2, but not a doubled 4.