Static Electricity Simulator (2D, Triboelectric Charging)

This 2D companion isolates the mechanics the 3D two-object spark demo does not: a draggable charged rod whose triboelectric charge you build up by choosing a real material pair and a rub duration, then use to pull light neutral objects — paper bits and a swinging balloon — purely through induced-charge Coulomb attraction, while a physically solved electroscope reads out the rod's actual charge via real leaf-deflection torque balance. Nothing here is a fixed animation: the charge accumulates with time constant and saturation, the pull on every object is computed from F = kq₁q₂/r² each frame from the rod's live position, and the electroscope angle comes from balancing gravity against electrostatic repulsion numerically.