What do both the field and the wall have in common?
The color, both the field and the wall are green.
    src        edge_attr  dst
0     0   to the left of   16
1     1   to the left of   18
2     1   to the left of    4
3     1  to the right of    5
4     1   to the left of   15
..  ...              ...  ...
62   18  to the right of    3
63   18  to the right of    1
64   18  to the right of   16
65   18  to the right of    8
66   18  to the right of    4

[67 rows x 3 columns]