+---+---+---+---+---+---+---+---+---+---+
        |   |                       |   |
+---+   +   +   +---+   +---+---+   +   +
|   |   |           |   |   |           |
+   +   +---+---+---+   +   +   +---+---+
|               |       |   |           |
+---+   +---+---+   +---+   +---+   +   +
|       |                   |       |   |
+   +---+   +---+---+---+---+   +---+   +
|           |                   |        
+---+---+---+---+---+---+---+---+---+---+