* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: 'Poppins', sans-serif;
}

body {
  background: linear-gradient(135deg, #667eea, #764ba2);
  color: #fff;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100vh;
}

h1 {
  margin-bottom: 20px;
  font-size: 2rem;
}

.game-container {
  display: grid;
  grid-template-columns: repeat(4, 100px);
  grid-gap: 15px;
  justify-content: center;
}

.card {
  width: 100px;
  height: 100px;
  background-color: #2d2d2d;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  cursor: pointer;
  transition: transform 0.3s;
  transform-style: preserve-3d;
  position: relative;
}

.card.flip {
  transform: rotateY(180deg);
}

.card .front,
.card .back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  border-radius: 10px;
}

.card .front {
  background-color: #fff;
  color: #333;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  transform: rotateY(180deg);
}

.card .back {
  background-color: #444;
}

#restartBtn {
  margin-top: 20px;
  padding: 10px 20px;
  font-size: 1rem;
  background-color: #fff;
  color: #333;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.3s;
}

#restartBtn:hover {
  background-color: #ddd;
}
.custom-link {
    margin-right: auto;
    display: inline-block;
    padding: 12px 28px;
    background: linear-gradient(45deg, #6a11cb, #2575fc);
    color: white;
    text-decoration: none;
    font-weight: 600;
    border-radius: 30px;
    box-shadow: 0 4px 15px rgba(38, 50, 56, 0.3);
    transition: background 0.3s ease, box-shadow 0.3s ease;
    font-family: Arial, sans-serif;
  }

  .custom-link:hover {
    background: linear-gradient(45deg, #2575fc, #6a11cb);
    box-shadow: 0 6px 20px rgba(38, 50, 56, 0.5);
    text-decoration: none;
  }