GOAL Manager

             ______________________
            |                      |
            | GOAL_Manager         |
            |_________             |
            |         |            |
 ---------->|  Post() |---------------------.----------.
            |_________|            |        |          |
            |                      |        |          |
            |                      |        |          | Add / Delete object
            |                      |        |          |
            |                      |        |          |
            |______________        |        |          |
            |              |       |        |          |
     .------|  Main Thread |       |        |          |
     |      |______________|_______|        |          |
     |                                      |          |
     |       _______________________________|_________\|/__________
     |      |                   ____________|_____________         |
     |      |                  |  __________|_____________|_       |
     |      | GOAL_Screen      | |  _______\|/______________|_     |
     |      |                  | | |   |           |          |    |
     |      |                  | | |   | Command() |----.     |    |
     |      |                  | | |   |___________|    |     |    |
     |      |                  | | |                    |     |    |
     |      |                  | | | GOAL_Object        |     |    |
     |      |                  | | |    ___________     |     |    |
     |      |                  | | |   |           |<---'     |    |
     |      |                  | | |   | Update()  |          |    |
     |      |                  | | |   |___________|<---.     |    |
     |      |                  | | |    ___________     |     |    |
     |      |                  |_| |   |           |    |     |    |
     |      |                    |_|   | Refresh() |----'     |    |
     |      |                      |___|___________|__________|    |
     |      |___________                    /|\                    |
     |      |           |                    |                     |
     '----->| Refresh() |--------------------'                     |
            |___________|                                          |
            |______________________________________________________|