CONST lx = 639, ly = 479, xl = 2.5, xm = 1.5, yl = -1, ym = 1, im% = 44, a = .777: b = .136
     CLS : RANDOMIZE TIMER: SCREEN 12
     DO
        x0 = (xm - xi) * RND(1) + xi: y0 = (ym - yi) * RND(1) + yi: x = x0: y = y0: f = 0
        FOR i% = 1 TO im%
          xx = (x * x - y * y) - a: y = 2! * x * y - b: x = xx
          IF (x * x + y * y > 4) THEN : f = -1: i% = im%
        NEXT i%
        IF (NOT (f)) THEN
          x = x0: y = y0
          FOR i% = 1 TO im% / 4
            xp = lx * (x - xi) / (xm - xi): yp = ly * (y - yi) / (ym - yi)
            CIRCLE (xp, yp), 1, 15: CIRCLE (lx - xp, ly - yp), 1, 15
            xx = (x * x - y * y) - a: y = 2 * x * y - b: x = xx
          NEXT i%
         END IF
      LOOP