1 digraph G {

     2     compound=true;

     3     rankdir=LR;

     4 

     5     gs [label="Game State"];    

     6     client [label="Client"];

     7     server [label="Server"];

     8     physics [label="Physics"];

     9     graphics [label="Graphics"];

    10 //    internet [label="Teh Internets", shape=polygon];    

    11 

    12     subgraph cluster0 {

    13         label = "Network";

    14 	{rank=source; client; server;}

    15 	client;

    16 	server;	

    17 	color = black;

    18     }

    19 

    20     subgraph cluster1 {

    21         label = "Game Engine";

    22 	{rank=min; gs; physics;}

    23 	gs;

    24 	physics;

    25 	color = black;

    26     }

    27 

    28     {rank=sink; input; graphics;}

    29  //   client->server [dir=both];

    30     client->server;

    31     server->client;

    32 

    33     gs->physics;	

    34     physics->graphics [ltail=cluster1];  

    35     input->gs [lhead=cluster1];    

    36 //   client->internet [ltail=cluster0];

    37 //   internet->server [lhead=cluster0];

    38 

    39     gs->server [lhead=cluster0,dir=both];

    40 }