Template:Proof/styles.css

.proof { 
	border: thin solid #aaa; 
	margin: 1em 2em; 
	padding: 0.5em 1em 0.4em;
}

.proof::after {
	content: "";
	display: table;
	clear: both;
}

.qed {
	float: right;
	clear: both; 
	margin-top: 0.2em;
	font-size: 1.2em;
}

@media (max-width: 500px) { 
	.proof {
		margin: 1em 0;
		padding: 0.5em 0.5em 0.4em;
	}
}