Game Mode

A game mode is the rules of a match. A level names its class, and opening the level constructs the mode with the options the transition supplied, builds the game state from the mode’s gameStateClass, and runs its beginPlay after every declared actor has begun play. The mode is the only object that adds players and bots, restarts their pawns, moves the match through its phases, and decides when the match is over.

GameModeClass

type GameModeClass = new () => GameMode;

A mode is constructed with no arguments, so a constructor sets the mode’s class fields and its own defaults. world, options, and state are assigned before beginPlay runs.

MatchPhase

type MatchPhase = "waiting" | "playing" | "over";

Phase	Meaning
waiting	The match is being set up. This is the phase a mode holds when it begins play.
playing	The match is running. GameState.elapsed accumulates only in this phase.
over	The match is decided.

The phase changes only through setPhase.

EndPlayReason

type EndPlayReason = "destroyed" | "level-closed";

Reason	Given to
destroyed	An actor and its components ending play because the actor was destroyed, and a component removed by detach.
level-closed	Every controller, actor, component, and game mode ending play because the world is closing.

GameMode

class GameMode {
  readonly world: World;
  readonly options: Readonly<Record<string, unknown>>;
  readonly state: GameState;
  readonly phase: MatchPhase;

  gameStateClass: new () => GameState;
  playerStateClass: new () => PlayerState;
  playerControllerClass: ControllerClass<PlayerController>;
  pawnClass: ActorClass<Pawn> | null;

  beginPlay(): void;
  tick(dt: number): void;
  endPlay(reason: EndPlayReason): void;

  addPlayer(options?: PlayerOptions): PlayerController;
  addBot(
    type: ControllerClass<AIController>,
    options?: BotOptions,
  ): AIController;
  restart(controller: Controller): Pawn | null;
  spawnPoint(controller: Controller): Transform;
  pawnDied(controller: Controller, pawn: Pawn): void;
  setPhase(phase: MatchPhase): void;
}

Member	Semantics
world	The world this mode governs.
options	Whatever world.open was given, or an empty object for the start level.
state	The world’s game state, the instance built from gameStateClass.
phase	The match phase. "waiting" when the mode begins play.
gameStateClass	Defaults to GameState. Read once, when the world is built.
playerStateClass	Defaults to PlayerState. Read on each addPlayer and addBot.
playerControllerClass	The controller addPlayer builds when its options name none.
pawnClass	The pawn restart spawns. null for a mode whose controllers possess nothing.
beginPlay	Runs after every declared actor has begun play. Where a mode adds its players and sets its phase.
tick	Runs once per frame, after every actor has ticked and after collision has been reported, so the mode decides the match from a settled world.
endPlay	Runs when the world closes, after every actor has ended play.
addPlayer	Builds the player state, the player controller, and the pawn, and possesses. Assigns the next free index when the options name none.
addBot	The same for an AI controller. A bot’s player state carries the next free index.
restart	Destroys the controller’s current pawn, spawns pawnClass at spawnPoint(controller), and possesses it. Returns null when pawnClass is null.
spawnPoint	Where restart places a pawn. The base implementation returns the center of the design field.
pawnDied	Runs when a possessed pawn is destroyed, after the pawn’s endPlay. The base implementation does nothing.
setPhase	Sets the phase, writes it onto the game state, and emits match:phase. Setting the phase it already holds emits nothing.

The base class’s beginPlay, tick, endPlay, and pawnDied do nothing, so a mode overrides only what it needs.

PlayerOptions

interface PlayerOptions {
  index?: number;
  name?: string;
  controller?: ControllerClass<PlayerController>;
  pawn?: ActorClass<Pawn> | null;
}

Field	Meaning
index	The index the player state carries. Absent, addPlayer assigns the next free index.
name	The name written onto the player state.
controller	The controller class to build. Absent, addPlayer builds playerControllerClass.
pawn	The pawn class to spawn and possess, in place of pawnClass. null adds a controller that possesses nothing.

BotOptions

interface BotOptions {
  name?: string;
  pawn?: ActorClass<Pawn> | null;
}

Field	Meaning
name	The name written onto the bot’s player state.
pawn	The pawn class to spawn and possess, in place of pawnClass. null adds a controller that possesses nothing.

addBot takes the controller class as its first argument, so BotOptions names no controller. A bot’s player state carries the next free index and sits in state.players alongside a player’s.

GameState

class GameState {
  readonly world: World;
  readonly players: readonly PlayerState[];
  phase: MatchPhase;
  elapsed: number;
}

Member	Semantics
world	The world this state belongs to.
players	Every player state, in index order, a bot’s alongside a player’s.
phase	The phase setPhase last wrote.
elapsed	Seconds accumulated while the phase is "playing".

elapsed is the match clock rather than the world clock. A game carries its own match figures by subclassing GameState and naming that subclass in gameStateClass.

PlayerState

class PlayerState {
  readonly index: number;
  readonly controller: Controller;
  name: string;
  score: number;
}

Member	Semantics
index	The participant’s index, assigned when the player or bot is added.
controller	The controller this state belongs to.
name	The participant’s display name.
score	The participant’s score.

A game carries its own per-player figures by subclassing PlayerState and naming that subclass in playerStateClass. The state is the durable half of a participant: it survives every respawn its controller performs.

Errors

Condition	Result
beginPlay throws while the start level is opening	engine.initialize rejects with the cause
tick throws under run	The error propagates to the host, and the loop schedules the next frame
tick throws under advance	advance rejects with the cause, and the remaining frames do not run

A throw under run leaves the loop alive, so one bad frame leaves the game running. A throw under advance stops at once, because a caller stepping an exact number of frames needs the failure rather than the frames after it.

Exports

GameMode, GameState, and PlayerState are exported as classes from @clockwyrks/structured-2d. GameModeClass, MatchPhase, EndPlayReason, PlayerOptions, and BotOptions are exported as types.