div{
  position:fixed;
  left: 50%;
  top: 50%;
  transform: translateX(-50%) translateY(-50%);
  
  width:80%;
  height:80%;
  
  background-color:blue;
  
  display:flex;
  justify-content: center;
  align-items:center
}

p{
  color:#fff;
  font-size:32px;
}