html, body {
height:100%;
margin: 0;
font-size: 95%;
background: #ccc;
}
.logo {
                margin-top: -244px;
                margin-left: -250px;
                position: absolute;
                top: 50%;
                left: 50%;
                width: 500px;
                height: 488px;
                border:none;
                }

@media screen and (max-width: 645px) {
img {width: 350px;}
.logo {
       width: 350px;
       height: 342px;
       margin-top: -175px;
       margin-left: -171px;
       }
}