void local fn DoIt
  long c = 0, x, y, w = 1

  CFArrayRef colors = @[fn ColorBlack,fn ColorRed,
  fn ColorGreen,fn ColorBlue,fn ColorMagenta,
  fn ColorCyan,fn ColorYellow,fn ColorWhite]

  window 1,, (0,0,384,240), NSWindowStyleMaskBorderless

  pen -1
  for y = 0 to 180 step 60
    for x = 0 to 384 - w step w
      rect fill (x,y,w,60), colors[c]
      c++
      if ( c >= len(colors) ) then c = 0
    next
    w++
  next
end fn

fn DoIt

HandleEvents