🧲 Magnetism (2D)

This 2D companion models each bar magnet as a pair of point poles and sums their inverse-square contributions the same way the 3D original does, just evaluated in a flat plane you can drag things across: bar magnets and a compass respond to mouse or touch, iron filings scattered across the field rotate to trace out the dipole shape, and adding a second magnet lets you see attraction and repulsion — plus the force between them — depending on which poles face each other.