Is the sand rough or smooth?
The sand is rough.
    src        edge_attr  dst
0     0   to the left of    1
1     1  to the right of    0
2     1  to the right of    9
3     1  to the right of    7
4     2   to the left of    8
5     6   to the left of    8
6     7          wearing    0
7     7   to the left of    8
8     7   to the left of    1
9     8  to the right of    7
10    8  to the right of    6
11    8  to the right of    2
12    9   to the left of    1