rem Julia set
WindowWidth = 640: WindowHeight = 400
graphicbox #julset.gbox, 0, 0, 639, 399
open "Julia set" for window as #julset
print #julset.gbox, "down"
x0 = -0.512511498387847167 : y0 = 0.521295573094847167
for xp = 0 TO 639
  for yp = 0 TO 399
    x = xp / 213 - 1.5: y = yp / 200 - 1
    iteration = 0
    maxIteration = 100
    while x * x + y * y <= 4 and iteration < maxIteration
      xtemp = x * x - y * y + x0
      y = 2 * x * y + y0
      x = xtemp
      iteration = iteration + 1
    wend
    if iteration <> maxIteration then c = int(iteration * 255 / maxIteration + .5) else c = 0
    print #julset.gbox, "color "; c; " "; c; " "; c
    print #julset.gbox, "set "; xp; " "; yp
  next yp
next xp
wait