This guy is playing the Rhythm Tengkou minigame “Samurai Slice” by slicing a beam of light with a samurai sword in real life. He set up a light sensor to a robotic finger, then slashes the beam of light with a samurai sword, which causes the light sensor to trigger the robotic finger to press a button.
Yes, Rhythm Tengoku is a Game Boy Advance game, and he’s playing it on a Nintendo DS, but remember, the DS Lite has a slot for GBA games, presumably built into the unit with the sole intention of doing something like this.
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