btn02.addEventListener(MouseEvent.ROLL_OVER, rolloverEffect);
btn02.addEventListener(MouseEvent.ROLL_OUT, rolloutEffect);
btn03.addEventListener(MouseEvent.ROLL_OVER, rolloverEffect);
btn03.addEventListener(MouseEvent.ROLL_OUT, rolloutEffect);
btn04.addEventListener(MouseEvent.ROLL_OVER, rolloverEffect);
btn04.addEventListener(MouseEvent.ROLL_OUT, rolloutEffect);