10 frame off

   clear area box: 5,5,15, 30
   for i=6 to 14
     print at i,7: repeat$('1', 20)
   next i
   ask window: current first$

   clear area box: 8,10,18, 35
   for i=9 to 17
     print at i,12: repeat$('2', 20)
   next i
   ask window: current second$

   clear area box: 11,15,20, 40
   for i=12 to 19
     print at i,17: repeat$('3', 20)
   next i
   ask window: current third$

   delay
   set window: current second$
   delay
   set window: current first$
   delay
   clear