Spin

"Spin your nails in the golden ratio!... then you should have the ability to harness the power of infinity."

- Gyro Zeppeli to Johnny Joestar,

The Spin (回転) is a supernatural phenomenon wielded by multiple key characters in Steel Ball Run and JoJolion.

It is a state of perfect or near-perfect rotation which produces a unique form of energy that can be applied for a multitude of uses. It's possible that the Spin is a counterpart to the Ripple power featured in the original timeline.

Summary
The Spin is a state of rotation defined by its closeness to perfection, that perfection being the Ōgon Chōhōkei (黄金長方形), more specifically the that is derived from the Rectangle, a mathematically endless spiral, and a feature said to be omnipresent in the surrounding nature and a fortiori in works of arts.

Unlike the average rotation, the Spin is persistent and produces more rotational energy than it takes to create. That rotational energy is transferred to nearby objects in the form of vibrations and can be wielded for a wide array of purposes.

The Spin is a specialty of the Kingdom of Naples. It is intensively used there either for medicine or for battle. All characters capable of performing advanced Spin techniques are either Neapolitan or have been taught by a Neapolitan.

Using the Spin
Because of its miraculous property, the Spin has been wielded as a technique by a chosen few at least since the Middle Ages from which several specialized skills have been derived.

Users of the Spin typically try to spin objects to follow as best they can the Golden Rectangle, creating a near endless rotation that may then create an infinite amount of rotational energy, before throwing said objects at a target. To do so, they apply a small force causing the object to Spin near perfectly, giving it an impulse of energy to start the rotation, and then let the rotation perpetuate itself. A bit of advice given to neophytes is to visualize the perfect rotation and then try to emulate it.

The Spin is deceptively and relatively easy to learn at the basic, as the novice Johnny Joestar manages to produce a conclusive Spin with a cork within a day of learning about the power's existence; however, it is extremely difficult to master. The Spin must be imbued into a medium that will keep on spinning and must be thrown so the object can transfer the energy through contact. Thus, a Spin user must be able to expertly aim and throw objects in order to hope for a result. One must also know the human body extremely well to exploit the effects of the Spin on people to the fullest. For instance the Zeppeli Family are trained as surgeons to use the Spin on criminals on death row, otherwise, the Spin may only result in a simple enhancement of destructive energy. Others like the members of Naples' royal guard only use a highly specialized application of the Spin on the human body.

General Use



 * The Spin naturally enhances the destructive power of a projectile and thus can be thrown to simply inflict damage. A Steel Ball imbued with the Spin can destroy great chunks of rocks. Wekapipo's satellites are also propelled with as much force as bullets, being able to tear Gyro's hand.
 * The Spin can affect the body to harden it and enable it to easily transmit energy somewhere else, granting supernatural but temporary sturdiness. It allowed Gyro to become bulletproof and withstand the blast of one of Boku no Rhythm wo Kiitekure's bombs and only harm his leg or Wekapipo to redirect the energy of a Steel Ball.
 * The Spin is partially used to take control of the projectiles it is imbued to. Thanks to this phenomenon, Users of the Spin have control over how their projectiles react and can aim better, yet also have the projectiles return to their hands so as to not waste them.
 * An object imbued with Spin can be used to reinforce the Spin of other projectiles, for instance increasing the effective range of the Steel Balls.
 * Spinning objects have a high rotation speed and thus can create a large amount of friction. Thus, they can maintain objects in place like a cape to function like a sail or unravel objects like a tree's bark. Steel Balls, in particular, are shown to create makeshift ropes, and even carve into metal to create bullets.