dom.js

initDomElements() {
    this.$canvas = document.querySelector("#" + this.canvasId);
    this.$score = document.querySelector("#puntaje");
    this.$btnPause = document.querySelector("#btnPausar");
    this.$btnResume = document.querySelector("#btnIniciar");
    this.$btnRotate = document.querySelector("#btnRotar");
    this.$btnDown = document.querySelector("#btnAbajo");
    this.$btnRight = document.querySelector("#btnDerecha");
    this.$btnLeft = document.querySelector("#btnIzquierda");
    this.$canvas.setAttribute("width", Game.CANVAS_WIDTH + "px");
    this.$canvas.setAttribute("height", Game.CANVAS_HEIGHT + "px");
    this.canvasContext = this.$canvas.getContext("2d");
}