html, body {
  margin: 0;
  padding: 0;
  height: 100%;
}

body {
  background-image: url("wallpaper.jpg");
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  font-family: Arial;
}

.overlay {
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  color: white;
  background: rgba(0,0,0,0.3);
}

h1 {
  font-size: 60px;
}