.difficulty-selector {
  text-align: center;
  padding: 60px 20px;
}

.difficulty-title {
  font-size: 2rem;
  color: var(--primary);
  margin-bottom: 30px;
}

.difficulty-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 20px;
  justify-content: center;
}

.difficulty-buttons .btn {
  min-width: 180px;
  padding: 20px 30px;
  font-size: 1.2rem;
}

.difficulty-buttons .btn span {
  font-size: 1.5rem;
}

.game-area {
  padding: 20px;
}

.card-grid {
  display: grid;
  gap: 15px;
  justify-content: center;
  max-width: 600px;
  margin: 0 auto;
}

.card-grid.pairs-4 {
  grid-template-columns: repeat(4, 1fr);
}

.card-grid.pairs-6 {
  grid-template-columns: repeat(4, 1fr);
}

.card-grid.pairs-8 {
  grid-template-columns: repeat(4, 1fr);
}

.memory-card {
  aspect-ratio: 1;
  perspective: 1000px;
  cursor: pointer;
}

.memory-card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transition: transform 0.5s;
  transform-style: preserve-3d;
}

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

.memory-card.matched .memory-card-inner {
  animation: pulse 0.5s ease;
}

.memory-card-front,
.memory-card-back {
  position: absolute;
  width: 100%;
  height: 100%;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.8rem;
  font-weight: 800;
  box-shadow: var(--shadow-md);
}

.memory-card-front {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  font-size: 2.5rem;
}

.memory-card-back {
  background: white;
  transform: rotateY(180deg);
  border: 3px solid;
}

.memory-card.matched .memory-card-back {
  opacity: 0.7;
}

.game-stats {
  display: flex;
  justify-content: center;
  gap: 40px;
  padding: 15px;
  background: var(--white);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  margin-top: 20px;
}

.stat-item {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.3rem;
  font-weight: 700;
}

.stat-icon {
  font-size: 1.5rem;
}

/* Responsive */
@media (max-width: 600px) {
  .card-grid {
    gap: 10px;
  }

  .memory-card-front {
    font-size: 2rem;
  }

  .memory-card-back {
    font-size: 1.4rem;
  }

  .difficulty-buttons {
    flex-direction: column;
    align-items: center;
  }

  .game-stats {
    gap: 20px;
  }

  .stat-item {
    font-size: 1.1rem;
  }
}

@media (max-width: 400px) {
  .memory-card-front {
    font-size: 1.5rem;
  }

  .memory-card-back {
    font-size: 1.1rem;
  }
}