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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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CSS

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CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

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JavaScript

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JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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HTML 

              
                - var nl = 4;

pre
	span.token--prop --grad-list
	span.token--punct :
	span.token--val: ul
		- for(var i = 0; i < nl; i++) {
			- var j = i%2, k = ~~(i/2);
			li
				span.token--func radial-gradient
				span.token--punc (
				span.token--args
					span.token--arg
						span.token--kwd circle
						span.token--kwd at
						span.token--num #{j*100}
						if j
							span.token--unit %
						| 
						span.token--num #{k*100}
						if k
							span.token--unit %
					span.token--punc ,
					span.token--arg
						span.token--func var
						span.token--punc (
						span.token--prop --stop-list
						span.token--punc )
				span.token--punc )
		- }
section
	h3 mask layers
	.a3d
		while nl--
			.layer
section
	h3 mask applied to a box
	.box
!

CSS 

              
                @import 'compass/css3';

$nl: 4;
$p: .5em;
$lh: 1.375;
$t: 12s;

$u: floor(100%/$nl/3);

$theme-dark: #222;
$theme-light: invert($theme-dark);

@mixin mask($m) {
	-webkit-mask: $m;
					mask: $m
}

* {
	margin: 0;
	padding: 0;
	list-style: none;
	color: inherit;
	font: inherit
}

body {
	--f: 1;
	height: 100vh;
	display: flex;
	flex-wrap: wrap;
	font: 1em trebuchet ms, verdana, sans-serif;
}

pre {
	overflow: hidden;
	position: relative;
	padding: $p;
	width: 100%;
	font: 1em/ #{$lh} consolas, monaco, monospace;
	color: $theme-light;
	
	&:before {
		position: absolute;
		z-index: -1;
		top: 0; right: 0; bottom: 0; left: 0;
		background: $theme-dark;
		animation: shift $t infinite;
		content: ''
	}
}

ul {
	display: flex;
	flex-direction: column-reverse;
	animation: shift $t infinite
}

@keyframes shift {	
	0% { transform: translatey(calc(var(--f)*#{-$nl*$lh*1em})) }
	
	@for $i from 0 to $nl {
		#{($i + 1/3)*3*$u}, #{($i + 1)*3*$u} {
			transform: translatey(calc(var(--f)*#{($i + 1 - $nl)*$lh*1em}));
		}
	}
}

li {
	margin-left: 2vw;
	max-width: 31em;
	animation: a $t infinite;
	
	&:nth-child(n + 2):after { content: ',' }
	
	&:nth-child(2n) { --s: 1 }
	
	@for $i from 0 to $nl {
		&:nth-child(#{$i + 1}) {
			animation-name: slide#{$i + 1};
		}
		
		@at-root {
			@keyframes slide#{$i + 1} {
				0%, #{($i + 1/3)*3*$u} {
					transform: translate(calc(var(--s, -1)*100%)) scale(.001)
				}
				#{($i + 2/3)*3*$u}, 100% {
					transform: none
				}
			}
		}
	}
}

section {
	flex: 1;
	overflow: hidden;
	position: relative;
	width: 50%; min-height: calc(100vh - #{5*$lh*1em} - #{2*$p});
	perspective: 21em;
	--f: .5;
	animation: shift $t infinite
}

h3 {
	font: 700 1.75em/ 1.5 kalam, comic sans ms, cursive;
	text-align: center;
}

div {
	position: absolute;
	top: 50%; left: 50%;
	width: 16em; height: 16em;
	max-width: 100%;
	transform: translate(-50%, -50%);
}

.token {
	&--prop { color: #dbbae5 }
	
	&--val {
		white-space: normal
	}
	
	&--func {
		color: #b7e3c0;
		
		&:before { content: ' ' }
	}
	
	&--kwd {
		color: #b8d0dd;
		
		&:after { content: ' ' }
	}
	
	&--num { color: #f8f087 }
	
	&--unit { color: #f39dd4 }
}

.a3d { transform-style: preserve-3d }

.layer {
	background: #000;
	animation: l $t infinite;
	
	&:nth-child(2n) { --s: 1 }
	
	@for $i from 0 to $nl {
		$x: ($i%2)*100%;
		$y: floor($i/2)*100%;
		$m: radial-gradient(circle at $x $y, 
						transparent 19%, #000 0);
		
		&:nth-of-type(#{$i + 1}) {
			-webkit-mask: $m;
							mask: $m;
			animation-name: layer#{$i + 1};
			
			&:after { animation-name: fade#{$i + 1} }
			
			@at-root {
				@keyframes layer#{$i + 1} {
					0%, #{($i + 1/3)*3*$u} {
						transform: 
							translate3d(calc(var(--s, -1)*100% - 50%), -150%, 2em) 
							scale(.001);
					}
					#{($i + 2/3)*3*$u}, 100% {
						transform: translate(-50%, -50%) 
					}
				}
				
				@keyframes fade#{$i + 1} {
					0%, #{($i + 2/3)*3*$u} {
						opacity: .99
					}
					#{($i + 1)*3*$u}, 100% {
						opacity: .001
					}
				}
			}
		}
	}
	
	&:after {
		position: absolute;
		top: 0; right: 0; bottom: 0; left: 0;
		background: #b53;
		animation: f $t infinite;
		content: ''
	}
}

@keyframes mask {
	0%, 100% { @include mask(none) }
	
	@for $i from 0 to $nl {
		$m0: ();
		$m1: ();
		$ac0: 0; $ac1: 1;
		$ar0: 1; $ar1: 1;
		
		@for $j from 0 to $nl {
			$x: ($j%2)*100%;
			$y: floor($j%2)*100%;
			
			@if $i == $j {
				@if $i == 0 { $ac0: 1; $ac1: 0 }
				@else { $ac1: 0; $ar0: 0 }
			}
			@elseif $i < $j { $ar0: 0; $ar1: 0 }
			
			$m0: radial-gradient(circle at $x $y, 
							rgba(#000, $ac0) 19%, 
							rgba(#000, $ar0) 0), $m0;
			$m1: radial-gradient(circle at $x $y, 
							rgba(#000, $ac1) 19%, 
							rgba(#000, $ar1) 0), $m1;
		}
		
		#{($i + 2/3)*3*$u} { @include mask($m0) }
		#{($i + 1)*3*$u} { @include mask($m1) }
	}
}

.box {
	display: flex;
	align-items: center;
	justify-content: center;
	background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/2017/17_05_a_amur_leopard_0.jpg);
	animation: mask $t infinite;
	
	&:after {
		color: #f90;
		font: 700 2em kalam, cursive;
		text-shadow: 2px 2px #000;
		content: 'Amur Leopard'
	}
}

@media (max-aspect-ratio: 4/5) {
	html { overflow-x: hidden; }
	
	body {
		flex-direction: column;
	}
	
	section {
		width: 100%; min-height: calc(50vh - #{2.5*$lh*1em} - #{$p});
	}
}
!

JS
!
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