This is a labelled toy model, not a flight simulator. One honest rule runs everything: every push has a push-back on two different things. The rocket throws countable gas pellets backward; each throw speeds the rocket up a little, and the tally shows the gas's backward momentum exactly matching the rocket's forward momentum. The arithmetic is exact - you can audit it throw by throw.
What is real: rockets really do work by throwing their own hot gas backward (the flame IS the thrown gas); they need nothing outside to push against, which is why they are the only engines that work in empty space; with the engine off and nothing rubbing, a coasting craft keeps its speed; throwing harder or carrying more gas both add speed, and the same pushes move a lighter craft more. NASA's own pages say all of this.
Left out on purpose: gravity and air (a real rocket near the ground fights both - we left them out so the push-pair can be seen alone), real gas as a smooth river instead of countable pellets, steering and stages. No real launches, locations, or personal details are used; nothing about you leaves this page.
Sources: NASA Space Place ("How Do We Launch Things Into Space?") and NASA Glenn ("Newton's Third Law: Action & Reaction", "Thrust"). Links are in the project readme.