* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

body {
  height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  background: #060ab2;
}

.header {
  display: block;
  width: 100%;
  text-align: center;
  background-color: #1c7ccc;
  padding: 20px;
}

.memory-game {
  width: 640px;
  height: 640px;
  margin: 50px;
  display: flex;
  flex-wrap: wrap;
  perspective: 1000px;
}

.memory-card {
  width: calc(25% - 10px);
  height: calc(33.333% - 10px);
  margin: 5px;
  position: relative;
  transform: scale(1);
  transform-style: preserve-3d;
  transition: transform 0.5s;
  box-shadow: 1px 1px 1px rgba(0, 0, 0, 0.3);
}

.memory-card:active {
  transform: scale(0.97);
  transition: transform 0.2s;
}

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

.front-face,
.back-face {
  width: 100%;
  height: 100%;
  padding: 20px;
  position: absolute;
  border-radius: 5px;
  background: #1c7ccc;
  backface-visibility: hidden;
}

.front-face {
  transform: rotateY(180deg);
}

#restartBtn {
  display: block;
  margin-top: 30px;
  margin-bottom: 50px;
  padding: 10px 20px;
  font-size: 1rem;
  border-radius: 10px;
}