#game-container {
  text-align: center;
  font-family: Arial, sans-serif;
  max-width: 600px;
  margin: 0 auto;
}
#grid {
  display: grid;
  grid-template-columns: repeat(4, 100px);
  gap: 10px;
  margin: 20px auto;
  max-width: 440px;
}
.card {
  width: 100px;
  height: 100px;
  background: #333;
  cursor: pointer;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.5s;
}
.card.flipped {
  transform: rotateY(180deg);
}
.card-face {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
  color: white;
}
.card-front {
  background: #007bff;
  transform: rotateY(180deg);
}
.card-back {
  background: #333;
}
#start-btn, #reset-btn {
  padding: 10px 20px;
  font-size: 16px;
  cursor: pointer;
  color: white;
  border: none;
  border-radius: 5px;
  margin: 10px;
}
#start-btn {
  background: #ff6f00;
}
#start-btn:hover {
  background: #e65a00;
}
#reset-btn {
  background: #28a745;
}
#reset-btn:hover {
  background: #218838;
}
#reset-btn:disabled {
  background: #ccc;
  cursor: not-allowed;
}
#message {
  font-size: 18px;
  color: red;
  margin: 10px 0;
}