* {
  box-sizing: border-box;
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  margin: 20px;
  background-color: #f0f7fa;
  text-align: center;
  color: #333;
}

header h1 {
  font-size: 2rem;
  margin-bottom: 5px;
}

.name-input-container {
  max-width: 400px;
  margin: 20px auto;
  padding: 15px;
  border: 2px solid #007bff;
  border-radius: 10px;
  background-color: #eef6fc;
  text-align: left;
}

.name-input-container h2 {
  text-align: center;
  margin-bottom: 20px;
}

.name-input-container label {
  display: block;
  margin-top: 12px;
  margin-bottom: 4px;
  font-size: 1.1rem;
}

.name-input-container input {
  width: 100%;
  padding: 8px;
  font-size: 1rem;
  border-radius: 6px;
  border: 1px solid #007bff;
  box-sizing: border-box;
}

.name-input-container button {
  margin-top: 15px;
  width: 100%;
  padding: 10px;
  font-size: 1.1rem;
  background-color: #007bff;
  border: none;
  color: white;
  border-radius: 6px;
  cursor: pointer;
  transition: background-color 0.3s;
}

.name-input-container button:hover {
  background-color: #0056b3;
}

.hidden {
  display: none;
}

#scoreboard {
  margin: 20px auto;
  font-size: 1.2rem;
  display: flex;
  justify-content: center;
  gap: 40px;
  font-weight: bold;
}

.game-board {
  max-width: 600px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 15px;
}

.card {
  width: 100%;
  height: 120px;
  border-radius: 10px;
  cursor: pointer;
  perspective: 800px;
  position: relative;
}

.card-front,
.card-back {
  position: absolute;
  width: 100%;
  height: 100%;
  border-radius: 10px;
  backface-visibility: hidden;
  top: 0;
  left: 0;
  user-select: none;
  transition: transform 0.5s linear;
  display: flex;
  justify-content: center;
  align-items: center;
  font-weight: bold;
  font-size: 2.5rem;
  color: white;
}

.card-front {
  background-color: #e0e7ef;
  color: #333;
  transform: rotateY(0deg);
  z-index: 2;
}

.card-back {
  transform: rotateY(180deg);
  z-index: 1;
}

.card.flipped .card-front {
  transform: rotateY(-180deg);
  z-index: 1;
}

.card.flipped .card-back {
  transform: rotateY(0deg);
  z-index: 2;
}

button#restart-btn {
  margin-top: 30px;
  padding: 10px 25px;
  font-size: 1.1rem;
  border: none;
  border-radius: 8px;
  background-color: #007bff;
  color: white;
  cursor: pointer;
  transition: background-color 0.3s;
}

button#restart-btn:hover {
  background-color: #0056b3;
}