Module state 

Typed game states with enter/exit/transition schedules.

A state set is any small value type (usually an enum) that is Eq + Hash; one State<S> resource holds the current value and one NextState<S> holds a pending change. Requesting a transition from any system is a write to NextState<S>; the sim applies it once per fixed step, before the step’s main schedule, so a transition never interleaves with gameplay.

Apply order for A -> B matches the reference (bevy_state):

1. OnExit(A) - the State<S> resource still reads A
2. State<S> = B
3. OnTransition { exited: A, entered: B }
4. OnEnter(B)

If an enter/exit system requests another transition, it is resolved on the same step, up to MAX_CHAIN links; beyond that the chain is dropped and the last state stands. That bound stops a self-triggering transition from spinning the step forever.

Determinism: transitions run inside the fixed step and in registration order, so a replay that requests the same transitions at the same ticks resolves them identically. Do not request transitions from a thread.

Structs

NextState

A pending transition. Writing here requests a change; the sim applies it before the next step’s main schedule.

State

The current value of a state set.

Constants

MAX_CHAIN

Most transition links a single step resolves before giving up.

Traits

States

A state set: a plain value used as a game state.

Functions

in_state

Run condition: only run the configured systems while the state is state.