Each bar magnet is modelled as a pair of point poles (N and S) a short distance apart. The field at any point is the vector sum of each pole's inverse-square contribution — the same dipole approximation used by the 3D original, just evaluated in a flat plane.
- Field lines are traced step-by-step, always following the local field direction from an N pole until they reach an S pole.
- Iron filings rotate to align with the local field direction (180°-symmetric, since a filing has no preferred end).
- The compass needle is spring-damped toward the local field angle, like a real magnetized needle settling.
- Two magnets with opposite poles facing each other attract; same poles facing repel — drag them together to see it.