If OpenWindow(0,0,0,500,250,"Window",#PB_Window_SystemMenu|#PB_Window_ScreenCentered)
  SetWindowLongPtr_(WindowID(0),#GWL_EXSTYLE,GetWindowLongPtr_(WindowID(0),#GWL_EXSTYLE) | #WS_EX_LAYERED)
  SetLayeredWindowAttributes_(WindowID(0), 0, (255 * 50) / 100, #LWA_ALPHA)
Repeat : Until WaitWindowEvent() = #PB_Event_CloseWindow
EndIf