system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how does the NES light gun Zapper work?
gpt
When you press the trigger, the whole screen goes black for 1 frame.  Then in the next frame, the target area lights up white.  The Zapper has a detector that tells the NES whether it has detected a black to white transition.  The NES then knows that the Zapper was pointed at a target.