DIM C AS STRING = "Hello World! ", SIZE AS USHORT = LEN(C)
DIM DIRECTION AS BYTE = 0
DIM AS INTEGER X, Y, BTNS
DIM HELD AS BYTE = 0

SCREEN 19

DO
 LOCATE 1, 1
 PRINT C

 GETMOUSE X, Y, , BTNS

 IF BTNS <> 0 AND HELD = 0 THEN
  'remember if it was pressed, to not react every frame
  HELD = 1
  IF X >= 0 AND X < SIZE * 8 AND Y >= 0 AND Y < 16 THEN
   DIRECTION = 1 - DIRECTION
  END IF
 ELSE
  HELD = 0
 END IF

 IF INKEY = CHR(255) + CHR(107) THEN EXIT DO

 IF DIRECTION = 0 THEN
  C = RIGHT(C, 1) + LEFT(C, SIZE - 1)
 ELSE
  C = RIGHT(C, SIZE - 1) + LEFT(C, 1)
 END IF

 SLEEP 100, 1
LOOP