DEFINT A-Z

DIM DYNAMIC ScreenMem(0:1999) AT &HB800  'color video segment

FOR L = 1 TO 25
  FOR I = 1999 TO 80 STEP -1
   IF ((ScreenMem(I) AND &H70FF) = 32) AND _
      ((ScreenMem(I-80) AND &H70FF)<>32) THEN

      X               = ScreenMem(I)
      ScreenMem(I)    = ScreenMem(I-80)
      ScreenMem(I-80) = X

    END IF
  NEXT
  DELAY .20
NEXT

BEEP
SLEEP