.memory-board {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--tile-gap);
  padding: var(--tile-gap);
  background: var(--board-bg);
  --smooth-corners: 5;
  --corner-radius: 72;
  mask-image: paint(smooth-corners);
  width: 100%;
  aspect-ratio: 1;
}

.memory-card {
  position: relative;
  aspect-ratio: 1;
  perspective: 600px;
  background: none;
  border: none;
  padding: 0;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  -webkit-user-select: none;
  user-select: none;
}

.memory-card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transition: transform 300ms ease, opacity 500ms ease;
  transform-style: preserve-3d;
}

.memory-card.flipped .memory-card-inner,
.memory-card.matched .memory-card-inner {
  transform: rotateY(180deg);
}

.memory-card-front,
.memory-card-back {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  --smooth-corners: 5;
  --corner-radius: 60;
  mask-image: paint(smooth-corners);
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  font-weight: var(--font-weight-bold);
}

.memory-card-front {
  background: var(--tile-color);
  color: var(--color-surface-raised);
  font-size: 2.5rem;
  font-weight: var(--font-weight-normal);
}

.memory-card-back {
  background: var(--tile-color);
  color: var(--color-primary);
  font-size: 2.5rem;
  transform: rotateY(180deg);
}

.memory-card.matched {
  pointer-events: none;
}

.memory-card.matched .memory-card-front {
  visibility: hidden;
}

.memory-card.matched .memory-card-inner {
  opacity: 0;
}

.memory-card:active .memory-card-inner {
  transform: scale(0.95);
}

.memory-card.flipped:active .memory-card-inner,
.memory-card.matched:active .memory-card-inner {
  transform: rotateY(180deg) scale(0.95);
}

@keyframes memory-solved-pop {
  0% { transform: rotateY(180deg) scale(1); }
  50% { transform: rotateY(180deg) scale(1.1); }
  100% { transform: rotateY(180deg) scale(1); }
}

.memory-card.solved-pop .memory-card-inner {
  animation: memory-solved-pop 350ms ease forwards;
}