body {
  font-family: sans-serif;
  text-align: center;
  background-color: #f0f0f0;
  padding: 20px;
}

h1 {
  margin-bottom: 20px;
}

.game-board {
  display: grid;
  grid-template-columns: repeat(4, 100px);
  grid-gap: 15px;
  justify-content: center;
  margin: 0 auto;
  max-width: 500px;
}

.card {
  width: 100px;
  height: 100px;
  background-color: #999; /* face-down color */
  border-radius: 10px;
  cursor: pointer;
  box-shadow: 0 0 5px rgba(0,0,0,0.2);
  background-size: cover;
  background-position: center;
  transition: background-image 0.3s ease;
}

.restart-btn {
  display: inline-block;
  margin-top: 20px;
  padding: 10px 30px;
  font-size: 1.1em;
  background: #4caf50;
  color: #fff;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  box-shadow: 0 2px 6px rgba(0,0,0,0.1);
  transition: background 0.2s;
}

.restart-btn:hover {
  background: #388e3c;
}

.home-btn {
  position: absolute;
  top: 20px;
  left: 20px;
  background: #fff;
  color: #333;
  border-radius: 6px;
  padding: 8px 18px;
  font-size: 1em;
  text-decoration: none;
  font-weight: bold;
  box-shadow: 0 2px 6px rgba(0,0,0,0.07);
  transition: background 0.2s, color 0.2s, border 0.2s;
  z-index: 1000;
}

.home-btn:hover {
  background: #4caf50;
  color: #fff;
  border-color: #388e3c;
}