didn't realize you were switching in the middle of things
this is directly from the turing help file on setscreen
"nooffscreenonly", "offscreenonly" Causes or (suppresses) output from being sent to the visible window. When the offscreenonly option is active, any text and graphics output is drawn to the offscreen buffer that is maintained for every Run window but not drawn to the screen. View.Update is then used to copy the entire contents of the offscreen buffer to the Run window. By allowing numerous drawing commands to be sent to the offscreen buffer and then updating the window at one time, it is possible to get smoother animation.