body{  
  background-color: mediumseagreen;
}
h1 { 
  color: darkgreen;
 font-family: sans-serif; 
 text-align: center; 
}  
#result {
  background-color: white;
}

#container {
  position: fixed;
  top: 50%;  left: 50%;
  transform: translate(-50%, -50%);
  background-color: lightgreen;
  border-radius: 2em;
  padding: 20px;
}