SCREEN 12
  CLS
  r3 = SQR(3) / 6
  ex = 550
  sx = 50
  sy = 200
  x = 1
  y = 0
  GOSUB po
  WHILE INKEY$ <> CHR$(13)
    IF RND(1) > .5 THEN
          x0 = .5 * x + r3 * y
          y0 = r3 * x - .5 * y
    ELSE
          x0 = .66666666# * x + .3333333#
          y0 = -.66666666# * y
    END IF
    x = x0
    y = y0
    GOSUB po
  WEND
  dummy$ = INPUT$(1)
  CLS
  END

po:
  PSET (x * ex + sx, sy - y * ex)
  RETURN