                                                                             
                                      ^ v                                    
                                      |                                      
                                      |                                      
   +---------------------------*-***********-*---------------------------+   
   |                      *****.......|.......*****                      |   
   |                  ****............|............****                  |   
   |                **................|................**                |   
   |             **...................|...................**             |   
   |            *.....................|.....................*            |   
   |          *.......................|.......................*          |   
   |         *........................|.........................*        |   
   |       *..........................|..........................*       |   
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   |    *.............................|.............................*    |   
   |   *..............................|..............................*   |   
   |  *...............................|...............................*  |   
   |  *...............................|................................* |   
   | *................................|................................* |   
   | *................................|................................* |   
   |*.................................|.................................*|   
   |*.................................|.................................*|   
   *..................................|..................................*   
   *..................................|..................................*   
   *..................................|..................................*   
---*----------------------------------+----------------------------------*--> u

