body {
  background: url("./img/game.png") no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}

header > h1 {
  color: white;
  position: relative;
  text-align: center;
  font-size: 80px;
}

.in-up {
  text-align: center;
}

#back {
  margin-right:100px;
  margin-top: 50px;
  font-size: 40px;
  border-radius: 40%;
}

#sign-in {
  font-size: 40px;
  border-radius: 40%;
  background-color: green;
  color: white;
}

.container > input {
  font-size: 40px;
}

.container {
  text-align: center;
}

.container {
  text-align: center;
  clear: both;
}