Set a stroke and fire.
The cannon
Ring ledger
Conservation
Circulation is constant by construction here, so it proves nothing. The impulse is the one that can fail — switch the induction law and watch it. Impulse tests the kernel and holds to roundoff even under this page’s cheap order-2 stepper; energy tests the integrator, so it drifts here and is tight only in the offline audit.
Read the speed out of the field
The formation window
What this measures
Wrong laws, on purpose
Every row is a plausible induction law. The margin is how much worse its impulse book closes than the honest kernel's.