body {
    font-family: Arial, sans-serif;
    text-align: center;
}

#game-board {
  display: grid;
  grid-template-columns: repeat(4, 120px);
  grid-template-rows: repeat(4, 120px);
  grid-gap: 10px;
  justify-content: center;
  margin: 30px auto;
}

.card {
  background-color: black;
  border-radius: 8px;
  cursor: pointer;
  align-content: center;
}

.card .card-content{
  visibility: hidden;
}

.card.flipped .card-content{
  visibility: visible;
}

.card.flipped.matched {
  background-color: greenyellow;
  pointer-events: none;
}