system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does the gun controller for Duck Hunt on NES work?
gpt
Everyone is missing an important point about this so I'll explain how it actually worked.

When you press the trigger, the screen goes black. The *entire* screen, for one frame (technically, one interlaced field).

*Then*, on the next frame (field, technically)  the target goes white. 

If there are multiple targets, only the first is replaced by a white box on the first frame; then on the next frame the second target is highlighted and so on.

Then the screen goes black again for a frame and then it returns to the normal display.

This all happens in a fraction of a second so it looks like it's all one frame. It is not.

The reason it is done this way is to prevent cheating. If you held the gun towards a light source you would always register a hit, if not for the initial black screen. The gun must detect a switch between black and white in the narrow window of time it's supposed to work. This prevents cheating by pointing at light sources.