#main h1 { position: fixed; left: -10000000px; top: -10000000px; }
#centerbox {
	display: table;
	min-height: calc(100vh - 25px);
	margin-left: auto; margin-right: auto;
	width: 100%; max-width: 450px;
}
#centerbox > * {
	display: table-cell;
	padding: 20px;
	vertical-align: middle;
}
#poweredby {
	display: table;
	width: 100%;
}
#poweredby > * {
	display: table-cell;
	font-size: 0.8em;
	padding: 0 20px 10px;
	vertical-align: middle;
}
#poweredby > *:last-child { width: 130px; }
@media screen and (max-width: 420px) {
	#centerbox { min-height: calc(100vh - 50px); }
	#poweredby, #poweredby > * { display: block; }
	#poweredby > * {
		box-sizing: border-box;
		padding: 0;
		text-align: center;
		width: 100%!important;
	}
	#poweredby > * + * { margin-top: 0.4em; padding-bottom: 10px; }
}