num ='s
#============#   12

                      line | num spaces | num .'s | num spaces 
|    <><>    |         1   |     4      |    0    |     4
|  <>....<>  |         2   |     2      |    4    |     2
|<>........<>|         3   |     0      |    8    |     0
                expression:  -2*line+6   4*line+4  -2*line+6

                      line | num spaces | num .'s | num spaces 
|<>........<>|         3   |     0      |    8    |     0
|  <>....<>  |         2   |     2      |    4    |     2
|    <><>    |         1   |     4      |    0    |     4
                expression:  -2*line+6   4*line+4  -2*line+6

#============# (same as first line)