def scatter
      sum_of_digits = @working_array.inject(:+).to_i
      @working_array = 10.times.collect do 
        @working_array.rotate!(spin ^ sum_of_digits).pop
      end
    end
def scatter
      sum_of_digits = @working_array.inject(:+).to_i
      @working_array = 10.times.collect do 
        @working_array.rotate!(spin ^ sum_of_digits).pop
      end
    end
Rearrange the order of each digit in a reversable way by using the
 sum of the digits (which doesn't change regardless of order)
 as a key to record how they were scattered