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Arm Rotor is R.O.B.'s side special move in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS / Wii U. R.O.B. spins its arms around at a downward angle as it moves forward, dealing multiple hits to any opponents in its path; in Super Smash Bros. for Nintendo 3DS / Wii U, the move ends with an uppercut that deals greater damage and knockback. Players can move in the opposite direction while the move is in use. The move also lasts longer if the player holds down the special attack button, and can reflect projectiles.
Two custom variants for Arm Rotor are also available in Super Smash Bros. for Nintendo 3DS / Wii U. The first is Reflector Arm, which makes it easier to reflect projectiles as R.O.B.'s arms spin completely horizontally rather than at an angle, but R.O.B. can no longer move during the attack. The second is Backward Arm Rotor, which has a shorter spin but allows the uppercut to happen more quickly.