this.el = document.createElement('li');
this.el.classList.add('pressed');
this.el.addEventListener('click', () => {
this.el.classList.remove('pressed');
this.el.textContent = num;
if (currentNum === parseInt(this.el.textContent, 10)) {
this.el.classList.add('pressed');
clearInterval(intervalId);;
for (let i = 0; i < 4; i++) {
this.panels.push(new Panel());
const board = document.getElementById('board');
this.panels.forEach(panel => {
board.appendChild(panel.getEl());
const nums = [0, 1, 2, 3];
this.panels.forEach(panel => {
const num = nums.splice(Math.floor(Math.random() * nums.length), 1)[0];
const timer = document.getElementById('timer');
timer.textContent = ((Date.now() - startTime) / 1000).toFixed(2);
const board = new Board();
const btn = document.getElementById('btn');
btn.addEventListener('click', () => {
intervalId = setInterval(() => {