Fill each row, column and 7-cell region with the digits 1-7 once each. The boundaries of the regions must be determined. Clues in the grid indicate some of the cells that can see at least two cells in its same region both horizontally and vertically. Every digit it sees horizontally ((including itself) is summed and every digit it sees vertically (including itself) is summed and these sums have been multiplied together to give the clue. Region boundaries stop the line of sight. eg A cell with a value of 49 must be a product of 7*7, so the cell containing that clue must be able to be part of a sum horizontally to 7 as well as vertically. So the cell could contain a 4 and have a 3 next to it horizontally; while it could have a 1&2 above and/or below it. Eg2 A cell with a value of 12 is the smallest clue possible and could be made a 1/2 in one direction and a 1/3 in the other direction.