style.css

body {
	line-height: 1.75;
}
a {
	color: inherit;
}

nav {
	display: flex;
	align-items: center;
	justify-content: space-between;
	width: 100%;
}
nav ul, .popup ul {
	margin: 0;
	padding: 0;
}

nav li {
	display: inline-block;
	vertical-align: middle;
}

.HLayout, .VLayout {
	display: flex;
}

.HLayout > .pane {
	background: black;
	color: white;
	border: 1px solid;
	display: block;
	overflow: auto;
	resize: both;
	margin: 5px;
	width: 75vw;
}

.VLayout {
	flex-direction: column;
}

.VLayout > .pane {
	background: black;
	border: 1px solid;
	display: block;
	overflow: auto;
	resize: both;
	margin: 5px;
	height: 240px;
	width: 420px;
}

h2 {
	margin: 0;
	padding: 0.5rem;
	background: linear-gradient(#000, #999);
	color: white;
	font-size: 100%;
}

.active h2 {
	background: linear-gradient(#00F, #99F);
}

.layer-container {
	position: relative;
	height: 600px;
}

.layer {
	position: absolute;
	top: 0;
	left: 0;
}

.popup {
	background: white;
	box-shadow: 0px 0px 10px black;
	border-radius: 5px;
	position: absolute;
	padding: 1em;
	width: 45vw;
	height: 40vh;
	resize: both;
	overflow: auto;
	z-index: 1;
	top: 0;
	left: 0;
	right: 0;
	bottom: 0;
	margin: auto;
}

.popup li {
	display: inline-block;
	width: 100%;
}

header {
	background: white;
	display: flex;
	padding: 0.5ex;
}

fieldset {
	font-size: small;
	overflow: auto;
}

label {
	display: block;
}

form > * {
	box-sizing: border-box;
	width: 100%;
}

#modal-background {
	position: absolute;
	width: 100vw;
	height: 100vh;
	top: 0;
	left: 0;
	right: 0;
	bottom: 0;
	margin: auto;
}