D-6

v-9.0
---
1. REFACTOR: --> handle nodes on the rect B
2. B_UL, pos = 1~4, next nodes

	==> done
D-6

v-9.1
---
1. REFACTOR: --> handle nodes on the rect B
2. B_UR, B_LR

	==> done
D-6

v-9.2
---
1. REFACTOR: --> handle nodes on the rect B
2. backwards

	==> done