body {
  font-family: Arial, sans-serif;
  margin: 0;               /* remove default margin */
  min-height: 100vh;       /* fill full viewport */
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background-color: #f7f7f7;
  color: #333;
  transition: background-color 1s; /* smooth color transition */
}

header {
  text-align: center;
  margin-bottom: 2rem;
}

img {
  display: block;
  margin: 0 auto;
  border: 2px solid #ccc;
  border-radius: 4px;
}