I think you could just have sticked with your first program, and solve it by a coordinate transformation.

3-1 to 1-0 is essentially the same like 2-1 to 0-0

               0-0
            1-0   1-1
         2-0   2-1   2-2
      3-0   3-1   3-2   3-3
   4-0   4-1   4-2   4-3   4-4
5-0   5-1   5-2   5-3   5-4   5-5
[download]

Though you would have ended with more readable code ... nah forget it! ;-)