@keyframes fadeIn {
  from { opacity: 0; transform: scale(0.8);}
  to { opacity: 1; transform: scale(1);}
}
@keyframes disappear {
  to { opacity: 0; transform: scale(0);}
}
.card {
  animation: fadeIn 0.3s ease-out;
  transition: all 0.2s;
}
.card:hover {
  transform: translateY(-3px);
  box-shadow: 0 10px 15px -3px rgba(0,0,0,0.1);
}
.selected {
  transform: scale(0.95);
  box-shadow: 0 0 0 3px rgba(59,130,246,0.5);
}
.matched {
  animation: disappear 0.5s forwards;
  pointer-events: none;
}
.difficulty-btn.active {
  transform: scale(1.05);
  box-shadow: 0 0 0 2px white;
}
.easy-btn { background-color: #10b981; }
.medium-btn { background-color: #f59e0b; }
.hard-btn { background-color: #ef4444; }