From the Super Mario Wiki
The Super Scope, known in PAL regions as the Nintendo Scope, is a light gun peripheral for the Super Nintendo Entertainment System. It fires an infrared beam that is picked up by a sensor placed on top of the television, and where on the screen it is aiming is determined by the sensor after calibrating the scope by shooting a test target screen.
The Super Scope is frequently depicted in-game as a type of gun. The weapon is featured in the game Yoshi's Safari, which is played using the actual Super Scope peripheral. Super Scopes also cameo as an in-game item used by Sniper Bills in Mario & Luigi: Superstar Saga, and the peripheral can be seen in the WarioWare: Touched! microgame, Gunslinger. In volume 8 of the Super Mario-Kun, Mario uses a Super Scope (sent by Princess Peach) to defeat the Kurokyura.
The Super Scope is featured as an item in the Super Smash Bros. series starting with Super Smash Bros. Melee, allowing players to fire energy balls at their opponents, either in dozens of small bullets or three huge charged up shots. When a player repeatedly shoots small blasts in a line, the opponent will be unable to move away when hit, but the player alone also cannot move while firing; in Super Smash Bros. Brawl, though, the player can walk and jump while firing the item.
Super Smash Bros. Melee
Super Smash Bros. Brawl
Super Smash Bros. for Nintendo 3DS / Wii U
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