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How does the Nintendo Light Gun work? (with video)

Filed Under Video Games |

Ahhh the old Nintendo Zapper, aka the Nintendo gun. An object of great joy and entertainment from our childhood. Something we played with day in and day out, but most of us had no clue how it worked. We’d make up stories about it shooting lasers off the tv or it changing the TV screen so that it knew where the gun was pointing, and accepted one of these highly uneducated explanations and continue with the game of Duck Hunt on the old NES, wondering why we could never shoot that stupid dog when he laughed at us.

In the past I’ve read explanations about how the Zapper actually worked, but that wasn’t enough for me. I wanted to see what was inside that plastic shell. So I found some tiny screwdrivers, exacerbated my mild carpal tunnel removing them and managed to get the thing apart. But before we get to the gory, err geeky pictures, a quick explanation for those that are still curious about how it works.

No, the gun does not shoot light. In fact it receives light. When you pull the trigger, the video game quickly changes the screen, so fast that most people don’t even notice it. By using the alterating of color and white light from the tv, the gun uses a photodiode to detect whether it’s scored a hit or not. So in short, the gun decides if you hit your target, not the Nintendo system. Here’s a brief explanation from Wikipedia:

When the trigger was pulled, the game blanked out the screen with a black background for one frame, then, for one additional frame, drew a solid white rectangle around the sprite the user was supposed to be shooting at. The photodiode at the back of the Zapper would detect these changes in intensity and send a signal to the NES to indicate whether it was over a lit pixel or not. A drop followed by a spike in intensity signaled a hit. Multiple sprites were supported by flashing a solid white rectangle around each potential sprite, one per frame.

So, with that said, here’s the picture of the gun mostly dismantled. Click on the image to jump to flickr to see the parts identified.

And here’s a video of what’s happening inside with that familiar “pang!” when you pull the trigger:

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