Some units of Brain Shift had a 'Tiger recommends Duracell' sticker attached to where the batteries are inserted. All sealed units had the stickers on the back of the packaging. This was because at that time, Tiger was allowed to promote Duracell batteries on their games. If the user press 'on' and 'pause' buttons on the front of the device and inserts one of the top right, bottom left and bottom right battery whilst there are three batteries in the unit, the game will enter test mode and play Happy Birthday To You using the sound that plays the melody during the game. Each color on the test mode will test different functions of the game. If the 'pause' button is pressed whilst in test mode, the user will be able to test the stick shift and the game will say the number followed by the colour.