Ответ подруге

function handleCardClick(event) {
  const card = event.currentTarget;

  if (card.classList.contains('flipped')) {
    return;
  }

  card.classList.add('flipped');

  const flippedCards = document.querySelectorAll('.main-game-card.flipped');

  if (flippedCards.length === 2) {
    let firstCardImg = flippedCards[0].querySelector('.front-card');
    let secondCardImg = flippedCards[1].querySelector('.front-card');
    setTimeout(() => {
      checkForMatch(firstCardImg, secondCardImg);
    }, 1000);
  }
}

function checkForMatch(firstCardImg, secondCardImg) {
  if (firstCardImg.src === secondCardImg.src) {
    firstCardImg.parentElement.classList.add('matched');
    secondCardImg.parentElement.classList.add('matched');
  } else {
    firstCardImg.parentElement.classList.remove('flipped');
    secondCardImg.parentElement.classList.remove('flipped');
  }
}