.........-                                          -.........
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..........                                     .    ..........
..........                                        . ..........
..........                                    . -.  ..........
.......... gull call.                    .      . - ..........
.......... ---------------------------------------- ..........
.........-                                          -.........
........-- the  seagull  is a metaphysics  trick; a --........
.......--^ world-builder's  shortcut, to  define  a ^--.......
......--^% section of reality  and  imply its size: %^--......
.....--^%@ place a  flock of birds  at the edge and @%^--.....
....--^%@£ make  their  calls  tesselate  over  the £@%^--....
...--^%@£# entire volume                            #£@%^--...
..--^%@£##                                          ##£@%^--..
.--^%@£### a seagull  can  be defined  by as little ###£@%^--.
..--^%@£## as  five  vertices;  six  triangles.  (i ##£@%^--..
...--^%@£# would  recommend  handling  in swarms of #£@%^--...
....--^%@£ at least a dozen birds.)                 £@%^--....
.....--^%@                                          @%^--.....
......--^%                                          %^--......
.......--^                                          ^--.......
........--                                          --........
.........-                                          -.........