anchor.diff:      swap 16 + swap
   ;
   
  -: turtleanim
  +: turtleanim  ( -- u ) \ the current turtle animation frame
       t 5 rshift 3 mod 50 +
   ;
   
  -: turtle3  ( x y -- )
  +: turtle3  ( x y -- ) \ draw three turtles
       turtleanim >r
       2dup r@ sprite
       r1 2dup r@ sprite
       r1 r> sprite
   ;
   
  -: turtle2  ( x y -- )
  +: turtle2  ( x y -- ) \ draw two turtles
       turtleanim >r
       2dup r@ sprite
       swap 16 + swap r> sprite
  -;
  -
  -: log1  ( x y -- )
  -    2dup            86 sprite
  -    r1 2dup         87 sprite
  -    r1              88 sprite
   ;
   
   : log ( length x y -- )
  
positive.code:     GD.calibrate
  
      game_setup
      1 done c!
      begin
          gameloop
      again
  
negative.code:     endcase
  ;
  
  : rotate_around ( x y a -- ) \ rotate sprite around (x, y)
      >r
      swap 65536 * swap 65536 *
      GD.cmd_loadidentity
      2dup GD.cmd_translate
      r> GD.cmd_rotate
  