Function tick 

pub fn tick(
    pool: &mut ParticlePool,
    emitter: &mut ParticleEmitter,
    gravity: &GravityForce,
    turbulence: &mut TurbulenceForce,
    collider: &ParticleCollider,
    color_over_life: &ColorOverLife,
    size_over_life: &SizeOverLife,
    dt: f32,
    rng: &mut Lcg,
)

Convenience function: run one full simulation tick on a pool.

Applies gravity, turbulence, integrates, resolves collisions, recycles dead particles, then emits new ones from the emitter.