function Runner(outerContainerId, opt_config) {
        // Singleton
        if (Runner.instance_) {
            return Runner.instance_;
        }
        Runner.instance_ = this;

        this.outerContainerEl = document.querySelector(outerContainerId);
        this.containerEl = null;
        this.snackbarEl = null;
        this.detailsButton = this.outerContainerEl.querySelector('#details-button');

        this.config = opt_config || Runner.config;

        this.dimensions = Runner.defaultDimensions;

        this.canvas = null;
        this.canvasCtx = null;

        this.tRex = null;

        this.distanceMeter = null;
        this.distanceRan = 0;

        this.highestScore = Number(window.localStorage.getItem("dinoHighestScore") || "0");

        this.time = 0;
        this.runningTime = 0;
        this.msPerFrame = 1000 / FPS;
        this.currentSpeed = this.config.SPEED;

        this.obstacles = [];

        this.activated = false; // Whether the easter egg has been activated.
        this.playing = false; // Whether the game is currently in play state.
        this.crashed = false;
        this.paused = false;
        this.inverted = false;
        this.invertTimer = 0;
        this.resizeTimerId_ = null;

        this.playCount = 0;

        // Sound FX.
        this.audioBuffer = null;
        this.soundFx = {};

        // Global web audio context for playing sounds.
        this.audioContext = null;

        // Images.
        this.images = {};
        this.imagesLoaded = 0;

        if (this.isDisabled()) {
            this.setupDisabledRunner();
        } else {
            this.loadImages();
        }
    }
T-Rex runner.
@param {string} outerContainerId Outer containing element id.
@param {Object} opt_config
@constructor
@export