Balancing equations — nothing is created or destroyed

Lavoisier's law: matter is conserved, so a chemical equation must have equal atoms on both sides. The engine balances in-domain — given CH4 + O2 -> CO2 + H2O it returns the true coefficients CH4 + 2 O2 -> CO2 + 2 H2O (https://narrowhighway.com/s/54db514fbdd51c90cad455bc773f8152da3b3eb6a53119da6ddb670c9464e23b), and it catches the unbalanced form as written (https://narrowhighway.com/s/3601aac39b6d8a85326b63ea32c72b7bf29f1e9c377ee7445edac90173386a4f). Balancing is bookkeeping: every carbon, hydrogen, and oxygen atom that goes in must come out. This one conservation law — mass in equals mass out — is why chemistry is exact and not alchemy, and it is the same conservation that runs the continuity equation and the sealed-ledger receipts of this very engine.