:root {
  --stone-color: #81676c;
  --homo-color: #e44d2e;
  --art-color: #0087BD;
  --agri-color: #71BC78;
  --civi-color: #7851A9;
  --industry-color: #708090;
}

body {
	width: 1001px;
	margin: 0 auto;
	font-family: sans-serif;
	padding: 1rem 0 2rem 0;
}

@media(min-width: 1000px) {
	.small-screens {
		display: none;
	}
}

h1 small {
	float: right;
	font-size: 1rem;
}

.key .ten, .key .thousand {
	display: block;
	margin-left: -1px;
}

.key .ten:after {
	display: block;
	width: 12px;
	height: 5px;
	content: ' ';
	background-size: 10px 10px;
	background-image:
		linear-gradient(to right, #333 2px, transparent 1px),
		linear-gradient(to bottom, #333 2px, transparent 1px);
}

.key .thousand:after {
	margin-bottom: 5px;
	display: block;
	width: 1002px;
	height: 5px;
	content: ' ';
	background-size: 10px 10px;
	background-image:
		linear-gradient(to right, #333 2px, transparent 1px),
		linear-gradient(to bottom, #333 2px, transparent 1px);
}

.era {
	background-size: 10px 10px;
	width: 100%;
}

.era > span {
	text-shadow: black 1px 0 10px;
	font-weight: bold;
	color: white;
	margin: 1rem 0 0 1rem;
}

.transition {
	position: relative;
	width: 100%;
	height: 10px;
}

.transition > span {
	position: absolute;
	background-size: 10px 10px;
	display: block;
	height: 100%;
}

.stone {
	background-image:
		linear-gradient(to right, #333 1px, transparent 1px),
		linear-gradient(to bottom, #333 1px, var(--stone-color) 1px);
}

.era.stone {
	height: 31000px;
}

.homo-sapiens {
	background-image:
		linear-gradient(to right, #333 1px, transparent 1px),
		linear-gradient(to bottom, #333 1px, var(--homo-color) 1px);
}

.era.homo-sapiens {
	height: 1300px;
}

.art {
	background-image:
		linear-gradient(to right, #333 1px, transparent 1px),
		linear-gradient(to bottom, #333 1px, var(--art-color) 1px);
}

.era.art {
	height: 600px;
}

.transition .art {
	width: 500px;
}

.transition .agriculture {
	left: 500px;
	width: 501px;
}

.agriculture {
	background-image:
		linear-gradient(to right, #333 1px, transparent 1px),
		linear-gradient(to bottom, #333 1px, var(--agri-color) 1px);
}

.era.agriculture {
	height: 50px;
}

.civilization {
	background-image:
		linear-gradient(to right, #333 1px, transparent 1px),
		linear-gradient(to bottom, #333 1px, var(--civi-color) 1px);
}

.era.civilization {
	height: 20px;
}

.transition.modern {
	height: 11px;
}

.transition.modern > span > span {
	position: absolute;
	top: 10px;
	border-left: 1px solid black;
	padding-left: 0.25rem;
}

.transition .civilization {
	width: 740px;
}

.transition .industry {
	left: 740px;
	width: 180px;
}

.industry, .ww2 {
	background-image:
		linear-gradient(to right, #333 1px, transparent 1px),
		linear-gradient(to bottom, #333 1px, var(--industry-color) 1px);
}

.transition .ww2 {
	left: 920px;
	width: 81px;
	overflow: visible;
	white-space: nowrap;
}