RFC: Li Engine unified simulation¶

Status: Draft
Track: PH-SIM
Vision: world-studio-vision.md

Problem¶

Industry forks game engines for CARLA, GROMACS GUIs, and slicers — drift and duplicate physics.

Proposal¶

One Li Engine core (li-world, li-scene, li-physics-*, li-render) with runtime profiles:

game | sim_rl | sim_automotive | sim_robotics | sim_additive | sim_scientific | sim_drug_design

li-sim exposes:

def sim_reset(world: SimWorld) -> unit
def sim_step(world: SimWorld, dt: float) -> unit

ml.rl.EnvPool calls sim_step — no duplicate Gym physics.

Li syntax¶

Use def for all new APIs. Do not document bare proc. extern proc only for FFI. Every exported def (and each extern proc) needs requires / ensures / decreases. The parser still accepts legacy bare proc in old trees only — reject that syntax in new Studio/game-dev docs and package code.

Phases¶

SIM-0 (this RFC) → SIM-1 step/reset → SIM-2 replay → SIM-3 RL hookup.