How does the gun on duck hunt work

When you pull the trigger, the TV very quickly goes black, and a flash of just the white duck appears. The photo sensor in the gun detects how far off you are from that particular white flash, and if it's centered. If the duck is centered in the photo sensor in the gun, then you obviously are pointed at the duck, and that duck goes through the death sequence. If the white duck is not centered, you are not pointing at the duck, therefore you miss. The game knows where you are aiming based upon the photo sensor in the gun, and it's position in relation to the ducks.