/**
 * GameLoop.ts — Sprint 6
 *
 * A simple deterministic game loop using setInterval for portability
 * across Node.js and browser environments. Exposes start/stop/pause/resume
 * and calls the provided `onUpdate(deltaMs)` callback each tick.
 *
 * Design choices:
 *  - Uses setInterval rather than requestAnimationFrame so tests can advance
 *    time without requiring a browser runtime.
 *  - `tickIntervalMs` defaults to 16ms (≈60 fps) but is overridable.
 *  - `pause()` keeps the interval alive but skips the onUpdate call,
 *    preserving the timing baseline so resume is seamless.
 *  - `frame` is incremented every time onUpdate fires (not every tick).
 */
export interface GameLoopOptions {
    /** Called each tick with deltaMs since last tick (paused ticks are skipped). */
    onUpdate: (deltaMs: number) => void | Promise<void>;
    /**
     * Interval between ticks in ms.
     * @default 16   (approx. 60 fps)
     */
    tickIntervalMs?: number;
    /**
     * Alias for tickIntervalMs, derived from fps.
     * If provided, takes precedence over tickIntervalMs.
     */
    targetFps?: number;
}
export declare class GameLoop {
    private _isRunning;
    private _isPaused;
    private _frame;
    private _handle;
    private _lastTime;
    private readonly onUpdate;
    private readonly intervalMs;
    constructor(options: GameLoopOptions);
    /** Whether the loop is currently running (not stopped). */
    get isRunning(): boolean;
    /** Whether the loop is paused (running but not ticking). */
    get isPaused(): boolean;
    /** Number of update calls since start() (skips paused frames). */
    get frame(): number;
    /**
     * Start the game loop.
     * If already running, this is a no-op.
     */
    start(): void;
    /**
     * Stop the game loop permanently.
     * Resets frame counter and running state.
     */
    stop(): void;
    /**
     * Pause the loop. `isRunning` stays true but `onUpdate` is not called.
     * The interval continues so resuming has minimal lag.
     */
    pause(): void;
    /**
     * Resume from a paused state. Resets the last-time baseline so the first
     * resumed tick doesn't produce an artificially large delta.
     */
    resume(): void;
    private _tick;
}
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