Нарисовать движение прямоугольника — QBasic(Бейсик)

SCREEN 12
PRINT : PRINT "  Press any key to show demo..."
DO: LOOP UNTIL INKEY$ <> ""
   FOR u = 0 TO 150
     LINE (320 - u, 200)-(200 - u, 280), 15, B
     LINE (320 + u, 200)-(440 + u, 280), 15, B
     WAIT &H3DA, 8
     WAIT &H3DA, 8, 8
     LINE (320 - u, 200)-(200 - u, 280), 0, B
     LINE (320 + u, 200)-(440 + u, 280), 0, B
   NEXT u