How DID Duck Hunt on your old NES work?

17 February 2006

4 Comments

Posted by:Ferry

Question: A friend and I were playing Nintendo, the original eight-bit system, and we played Duck Hunt, a game that requires a “light gun.” I was wondering: How exactly does the Nintendo game “know” where you are pointing the gun on the screen when you shoot ducks?!? Very mind-boggling! –Matt

Cecil answers: You’re going to give yourself such a smack when you hear this one. Stripped of the high-tech accoutrements (by 1980s standards, anyway), it’s the oldest trick in the book. You think you’re using the gun to shoot at the TV, right? But really the TV is shooting the gun.

Here’s what happens…

You shoot at a duck, which appears on an ordinary TV screen. The gun is connected to the game console; pressing the trigger blackens the screen, then causes a duck-shaped white target to appear momentarily. If your aim is true, a photo sensor in the gun detects the shift from dark to light, and bingo–dead duck. In short, the TV emits the light pulse and the gun detects it, not the other way around.

For technical details, see howstuffworks, which includes a link to Nintendo’s 1989 patent on the technology. The patent explains how the dark-to-light shift prevents you from cheating by pointing the gun at a steadily shining light source, a weakness of earlier light guns. You’ll also learn how multiple targets can appear on the screen at the same time and how more advanced systems can indicate on the screen exactly where your shot “hit.”