DOOM BSP (XMAS) TREE :p

                     . * .
                    (IDKFA)
                  ---\ | /---
                      \|/
                  ( ROOT NODE )
                  ( Partition )
                 /`--...___...-`\
                /                \
               /                  \
        o--( Node 1 )--o      o--( Node 2 )--o
          /  Front   \          /   Back   \
         /      |     \        /      |     \
        /       o      \      /       o      \
   [SUBSECTOR]    ( Node 3 )     [SUBSECTOR]
   | (Leaf A)|    /        \     | (Leaf B)|
   |_________|   /          \    |_________|
     [SEGS]     /            \     [SEGS]
    ( Gift ) [SUBSECTOR]  [SUBSECTOR] ( Gift )
             | (Leaf C)|  | (Leaf D)|
             |_________|  |_________|
               [SEGS]       [SEGS]