Resonance Disc

The Resonance Disk is an item introduced in Risk of Rain 2

The item grants charge on kill, and when full, fires a projectile dealing  damage, while also piercing enemies. Afterwards, it creates an explosion dealing  damage, ending with the original projectile flying back towards the user, dealing   damage along the way.

Math
While holding the Resonance Disc kills generates  spin, visible by the dot in the model flying around. Spin decays over time. Every th of a second,  ''. In short, the spin'' decays faster the longer time between kills.

Spin, in turn, generates charge. Charge does not decay. At 100% charge, the resonance disc checks all enemies within the blast radius of its nearest target to see if it can hit more enemies by targeting one of them instead. After selecting a target, it will fire according to the earlier description.

How much charge is generated from spin is dependent on time since the last kill, and the current spin used as a vertical velocity with   gravity (so upwards).

Tips

 * The Resonance Disc will also attack any nearby clay pots or barrels, which can prove fatal if you're in close proximity to one.

Trivia

 * Resonance Disc is Risk of Rain 2 equivalent to the Risk of Rain 1 item, Laser Turbine and is actually referred to as the  in the code.