html, body {
  height: 99%;
}

.buttonspace {
	position: absolute;
	top:40%;
	left:40%;
	text-align:center;
	vertical-align:middle;
	width:550px;
	margin: auto;
	padding: 10px;
}


@media (max-width: 480px) {
   #container {
        top: 55%; /* IMPORTANT */
        left: 50%; /* IMPORTANT */
        display: block;
        position: absolute;
        width: 750px;
        xheight: 417px;

        margin-top: -208.5px; /* HALF OF THE HEIGHT */
        margin-left: -375px; /* HALF OF THE WIDTH */
    }
}

.field { top:50%; height:35px; width:200px; }
.btn {height:35px;width:100px;}
.ok { background-color:lightgreen;}
.nok { background-color:red;}
.hidden {
	filter: blur(4px);;	
}