VDU 23,22,212;40;16,32,16,128
      txt$ = "Hello World! "
      direction% = TRUE
      ON MOUSE direction% = NOT direction% : RETURN
      OFF
      REPEAT
        CLS
        PRINT txt$;
        IF direction% THEN
          txt$ = RIGHT$(txt$) + LEFT$(txt$)
        ELSE
          txt$ = MID$(txt$,2) + LEFT$(txt$,1)
        ENDIF
        WAIT 20
      UNTIL FALSE