Feed a sheep, rule the world.

              message ::== "(" <message-part> ")"
         message-part ::== <*-message>
         tick-message ::== "tick"
        mouse-message ::== "mouse " xcoord " " ycoord
 server-mouse-message ::== "mouse " id " " xcoord " " ycoord
        sheep-message ::== "sheep " id " " xcoord " " ycoord " "
                           sheep-name " " state
       rename-message ::== "rename " id " " sheep-name
    gen-sheep-message ::== "gen-sheep"
       flower-message ::== "flower " xcoord " " ycoord
server-flower-message ::== "flower " id " " xcoord " " ycoord
        fence-message ::== "fence " xcoord " " ycoord " " width " " height
   id, xcoord, ycoord,
        height, width ::== non-negative integer
    sheep-name, state ::== string (can be delimited with double quotes)

Server-to-client messages: sheep-message, server-mouse-message, server-flower-message

Client-to-server messages: mouse-message, rename-message, gen-sheep-message, flower-message