/* Basic reset */
* { box-sizing: border-box; margin:0; padding:0; }
body { font-family: Arial, sans-serif; background:#fafafa; display:flex; flex-direction:column; align-items:center; }

/* Header */
header { text-align:center; margin:20px; }
.stats { margin-top:8px; font-size:0.9rem; }

/* Board */
.board {
  display: grid;
  gap: 12px;
  max-width: 800px;
  width: 100%;
  grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
}

/* Card */
.card {
  perspective: 1000px;
  cursor: pointer;
}
.card-inner {
  position: relative;
  width: 100%;
  padding-top: 100%; /* square */
  transform-style: preserve-3d;
  transition: transform 0.6s;
}
.card.flipped .card-inner { transform: rotateY(180deg); }

.card-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  border-radius: 8px;
  display:flex; align-items:center; justify-content:center;
}
.card-back {
  background:#2196F3;
}
.card-front {
  background:#fff;
  transform: rotateY(180deg);
  border: 2px solid #ddd;
}