This — undefined в стрелочной функции?

const cards = document.querySelectorAll('.memory-card');

let hasFlippedCard = false;
let firstCard, secondCard;

const flipCard = (e) =>  {
    const card = e.currentTarget;
    card.classList.add('flip');

    if (!hasFlippedCard) {
        hasFlippedCard = true;
        firstCard = this;
        return;
    }
    secondCard = this;
    hasFlippedCard = false;
    checkForMatch();
};

const checkForMatch = () => {
    if (firstCard.dataset.color === secondCard.dataset.color) {
        removeFlipCards();
        return;
    }
    unFlippedCards();
};

const removeFlipCards = () => {
    firstCard.style.display = 'none';
    secondCard.style.display = 'none';
};

const unFlippedCards = () => {
    setTimeout(() => {
         firstCard.classList.remove('flip');
         secondCard.classList.remove('flip');
     }, 1500);
};

 cards.forEach(card => card.addEventListener('click', flipCard));