body {
  font-family: 'Arial', sans-serif;
  text-align: center;
  background-color: #f0f8ff;
  margin: 0;
  padding: 20px;
}

h1 {
  color: #FF6B6B;
  font-size: 3em;
  margin-bottom: 20px;
  text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
  background: linear-gradient(45deg, #FF6B6B, #4ECDC4);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  animation: gradient 3s ease infinite;
  background-size: 200% 200%;
}

@keyframes gradient {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

.btn {
  padding: 15px 40px;
  color: white;
  border: none;
  border-radius: 50px;
  font-size: 1.2em;
  cursor: pointer;
  transition: all 0.3s;
  box-shadow: 0 4px 15px rgba(0,0,0,0.2);
  margin: 10px;
}

#startBtn {
  background: linear-gradient(45deg, #4ECDC4, #FF6B6B);
}

#startBtn:hover {
  background: linear-gradient(45deg, #FF6B6B, #4ECDC4);
  transform: translateY(-5px);
  box-shadow: 0 7px 20px rgba(0,0,0,0.3);
}

.difficulty-btn {
  background: #3498db;
  width: 200px;
}

.difficulty-btn:hover {
  background: #2980b9;
  transform: translateY(-3px);
  box-shadow: 0 6px 15px rgba(0,0,0,0.3);
}

.return-btn {
  background: #e74c3c;
  margin-top: 20px;
}

.return-btn:hover {
  background: #c0392b;
  transform: translateY(-3px);
  box-shadow: 0 6px 15px rgba(0,0,0,0.3);
}

.play-again-btn {
  background: #2ecc71;
}

.play-again-btn:hover {
  background: #27ae60;
  transform: translateY(-3px);
  box-shadow: 0 6px 15px rgba(0,0,0,0.3);
}

.screen {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 80vh;
}

#startScreen {
  background-color: rgba(255,255,255,0.9);
  border-radius: 20px;
  padding: 40px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.1);
}

#difficultyScreen, #gameScreen, #endScreen {
  display: none;
  background-color: rgba(255,255,255,0.9);
  border-radius: 20px;
  padding: 40px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.1);
}

.game-grid {
  display: grid;
  gap: 10px;
  margin: 20px auto;
}

.card {
  width: 80px;
  height: 80px;
  background-color: #6c5ce7;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2em;
  color: white;
  cursor: pointer;
  transition: all 0.3s ease;
  transform-style: preserve-3d;
  box-shadow: 0 4px 8px rgba(0,0,0,0.2);
}

.card:hover {
  transform: scale(1.05);
  box-shadow: 0 6px 12px rgba(0,0,0,0.3);
}

.card.flipped {
  transform: rotateY(180deg);
  background-color: #fff;
  color: #333;
}

.card.matched {
  background-color: #2ecc71;
  transform: rotateY(180deg);
  pointer-events: none;
}

.game-info {
  margin-bottom: 20px;
  font-size: 1.2em;
}

.timer, .moves {
  display: inline-block;
  margin: 0 15px;
  padding: 8px 15px;
  background-color: #f1c40f;
  border-radius: 20px;
  color: #333;
  font-weight: bold;
}

.rules-container {
  max-width: 600px;
  margin: 30px auto;
  padding: 20px;
  background-color: rgba(255, 255, 255, 0.8);
  border-radius: 15px;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
  text-align: left;
}

.rules-container h3 {
  color: #6c5ce7;
  margin-top: 20px;
  border-bottom: 2px solid #6c5ce7;
  padding-bottom: 5px;
}

.rules-container p {
  margin: 10px 0;
  line-height: 1.5;
}

.best-score {
  display: inline-block;
  margin: 0 15px;
  padding: 8px 15px;
  background-color: #6c5ce7;
  border-radius: 20px;
  color: white;
  font-weight: bold;
}