How do you use knuckles sunglasses in sonic adventure 2 battle

Stand still and press Y to change the B action to Sunglasses press B to put them on now you can find secret items keep in mind they come off anytime you press A or X you can have these on while underwater but if you press A or X they will come off. Also the screen will turn blue try to ignore that its a mechanic that's kinda letting you see what knuckles sees basically and you do need this item for hard mode missions for his stages.