What's the floor made of?
The floor is made of concrete.
    src        edge_attr  dst
0     1               by   12
1     1  to the right of   13
2     3               on    4
3     3  to the right of   13
4     5  to the right of   13
5     6  to the right of   12
6     6               on    8
7     6  to the right of   13
8     6  to the right of    9
9     8  to the right of    9
10    8  to the right of   13
11    8  to the right of   12
12    9  to the right of   13
13    9   to the left of    8
14    9   to the left of    6
15   12   to the left of    8
16   12   to the left of    6
17   13   to the left of    6
18   13   to the left of    8
19   13   to the left of    3
20   13   to the left of    9
21   13   to the left of    1
22   13               of   12
23   13   to the left of    5