body {
   background: #3397ff;
   line-height: 1.5em;
}

main {
   position: absolute;
   top: calc(50% - 200px / 2);
   left: calc(50% - 200px / 2);
   width: 200px;
   height: 200px;

   background: rgba(0, 0, 0, 0.4);
   color: #fff;
   font-size: 16px;
   text-transform: uppercase;
   display: flex;
   align-items: center;
   justify-content: center;
}