You set the start. Gravity writes the rest.

Nothing here is steered. You choose how many bodies, how far apart and how fast the cloud turns, and everything after that follows from Newtonian gravity and a fixed timestep. The competition being watched is the oldest one in astrophysics: gravity pulling inward against rotation and random motion holding outward. Turn the rotation up and the same cloud stops collapsing.

This is the one module whose determinism is structural rather than contained. An N-body system is chaotic, so a one-ulp disagreement between two browsers would not stay small — it would grow until they disagreed about where the bodies are. So the engine contains no approximated primitive at all: there is no Math.sqrtin it, no exponent operator, no trigonometry. Everything is exact IEEE arithmetic, and the server's trajectory is your trajectory bit for bit.

A toy in its own units, with softened gravity and at most twelve bodies. What it shows about the competition between gravity and rotation is real; it is not a simulation of any particular cluster, and its numbers are not anyone's measurements.