html {
  height: 100%;
  width: 100%;
}

.game {
  width: 100%;
  aspect-ratio: 16/9;
  background-image: url('background.png');
  background-size: cover;
  display: grid;
  grid-template-rows: repeat(3,1fr);
  grid-template-columns: repeat(3,1fr);
}

.card {
  background: white;
  border: 1px solid rgba(0,0,0,.15);
  cursor: pointer;
  padding: .5rem;
  text-align: center;
  display: grid;
  place-items: center;
}