body {
  margin: 0;
  font-family: Arial, sans-serif;
  background: #000;
  color: #fff;
  text-align: center;
  padding: 20px;
}
header {
  margin-bottom: 20px;
}
.card {
  display: inline-block;
  padding: 20px;
  margin: 10px;
  border-radius: 10px;
}