State

This chapter introduces a simple state machine to organize game flow (menu → playing → paused → game over). Instead of one giant loop, each state owns its own update and render behavior.

State machine (lib, ch08)

The StateMachine stores named states and manages transitions:

• add(state) registers a state.
• set(name) switches state and calls exit/enter hooks.
• update() and render() forward to the active state.

Each state conforms to this interface:

export interface GameState {
	name: string;
	enter?(prev?: GameState): void;
	exit?(next?: GameState): void;
	update(deltaTime: number): void;
	render(): void;
}

Wiring the engine to state

CH08 overrides update() and render() to delegate to the state machine:

protected override update(deltaTime: number): void {
	this.stateMachine.update(deltaTime);
}

protected override render(): void {
	this.stateMachine.render();
}

That keeps state‑specific logic out of the engine loop.

Why a state machine?

Beginner‑friendly reason: it prevents “if‑else soup.” Instead of sprinkling if (paused) checks everywhere, each state owns its own rules. You read one block and understand exactly what happens in that mode.

Enter/exit hooks

enter() and exit() are perfect for one‑time transitions:

• Show or hide UI layers.
• Reset timers.
• Spawn or clear entities.

This keeps those actions from repeating every frame.

States in this chapter

• menu: waits for Enter, shows title text.
• playing: runs the normal gameplay update/render.
• paused: overlays pause UI, resumes on p.
• gameover: shows score and waits for Enter.

Each state is a small object with update and render callbacks, plus optional enter/exit for UI toggles.

Resetting the game

When the user starts a new run, resetGame():

• resets score, lives, and asteroid list
• clears entities via entityManager.clear()
• spawns a new player and asteroids

This makes the state transitions clean and predictable.

Pattern to remember

Use state machines for flow, and entities/systems for behavior. It keeps your code organized as features grow.

Library changes

• Added lib/State with GameState and StateMachine.
• Engine remains unchanged except for minor support that enables this pattern.