12:34 am
jackt
Check your premises. Two solutions = input error
5:17 am
doseffing
Andy... the unique rectangles rule only applies when two of the cells are in the same box and the other two are in another box. If the cells are in four different boxes then you must rely on some other cells forcing one of the cells in the rectangle to take on a particular value. If the other cells don't force the rectangle then the puzzle will be invalid because it doesn't have a unique solution. I learned that one the hard way.
