.board {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  margin: 0 auto 20px;  
  width: 100%;
  max-width: 460px;     
}

.card {
  position: relative;
  width: 100%;
  padding-top: 100%;   
  perspective: 600px;
  cursor: pointer;
  max-width: 80px;      
}

.card-inner {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  transition: transform 0.4s;
  transform-style: preserve-3d;
}

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

.card-front,
.card-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  border-radius: 6px;    
}


.card-front {
  background-color: #ffffff;
  border: 2px solid #ccc;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 24x;      
}

.card-back {
  background-color: #4a90e2;
  transform: rotateY(180deg);
}

.countdown-container {
  text-align: center;
  font-size: 32px;
  font-weight: bold;
  margin-bottom: 15px;
}

.game-controls {
  margin: 20px 0;
  text-align: center;
}

.game-controls button {
  padding: 8px 16px;
  font-size: 16px;
  cursor: pointer;
}

.stats {
  margin-bottom: 15px;
  font-size: 16px;
  text-align: center;
}

.modal[hidden] {
  display: none !important;
}

.modal {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.5);
  display: flex;              
  justify-content: center;
  align-items: center;
  z-index: 1000;
}

.modal-content {
  background-color: #fff;
  padding: 20px;
  border-radius: 8px;
  text-align: center;
  min-width: 280px;
}

.modal-content p {
  font-size: 18px;
  margin-bottom: 10px;
}

.modal-content button {
  margin: 5px;
  padding: 8px 16px;
  font-size: 14px;
  cursor: pointer;
}