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Making Time and Chance Deterministic

· 2 min read
The reTS project
reverse-engineering → modernization

An RTS simulation cannot be reproduced exactly if “random” means whatever the host platform happens to provide, or if timers depend on wall-clock time. The second foundation milestone gave reTS its own faithful answers to both problems.

Last verified against the project oracle: 2026-07-15.

The same seed must mean the same game​

The original randomizer maintains a 250-word state table. Each draw mutates that table with wrapping integer operations; ranged draws use an inclusive interval and a rejection mask rather than a simple remainder. Signed shifts also matter. Replacing any of those details with a standard Rust generator would produce perfectly good randomness—and the wrong match.

reTS now reproduces the raw stream, inclusive ranged values, and floating-point draws from a known seed. The active sequence is the same across Tiberian Sun, Red Alert 2, and Yuri's Revenge even though the older game's object layout is a different size.

A timer is frame state​

The engine's common timers are compact state machines driven by the current simulation frame. An inactive sentinel distinguishes a stopped timer from a running one. Pausing first calculates and stores the remaining duration; resuming records a new start frame. Expiration clamps the visible remainder at zero, while the internal subtraction deliberately tolerates the signed frame counter wrapping around.

Tiberian Sun names the freeze and thaw operations Stop and Start. The later games call them Pause and Resume. The recovered state transition is otherwise the same.

A useful save-game surprise​

The research also found a behavior that future save/load work must preserve: the scenario random stream is read from saved data and then reconstructed from seed zero. reTS does not implement that complete save path yet, but the unexpected reset is now a testable requirement rather than a tempting “bug fix.”

Randomness and time are invisible when they work. That is precisely why they had to land early: movement choices, combat rolls, AI decisions, replays, and multiplayer synchronization will all depend on them producing the same answer on every machine.