* {
	box-sizing: border-box;
	margin: 0;
}
body {
	background: rgba(0, 0, 200, 0.4);
}
#menu {
	margin: 30px auto;
	width: 60%;
}
.header {
	margin-top: 30px;
	background: #ccf;
	padding: 0.5em;
	border-radius: 1.3em;
	transition-property: height;
	transition-duration: 3s;
}
.header * {
	display: none;
}
.header *:first-child {
	border: 0;
	padding: 0;
	background: inherit;
	display: block;
}
.header:hover * {
	transition-property: height;
	transition-duration: 3s;
	display: block;
}
.header * {
	font-size: 1em;
	border: 1px solid green;
	border-radius: 1em;
	margin-top: 10px;
	background: #cfc;
	padding: 0.5em;
	text-align: center;
	text-decoration: none;
	color: #000;
}
.header *:first-child {
	margin-top: 0;
}
.header a:visited {
	background: #0f0;
}
.header a:hover {
	background: #0b0;
}
.header a:active {
	background: green;
}