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Insecure Resource

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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

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <form>
	<section>
		<input id='a0' type='range'/>
		<label for='a0'>--a0: <output for='a0'>.5</output></label>
	</section>
	<section>
		<input id='a1' type='range'/>
		<label for='a1'>--a1: <output for='a1'>.5</output></label>
	</section>
</form>

<main>
	<figure>
		<img src='https://s3-us-west-2.amazonaws.com/s.cdpn.io/2017/17_05_a_amur_leopard_14.jpg' alt='Amur leopard staring the camera with an intrigued look, as if it was preparing to strike'>
		<figcaption>two layers</figcaption>
	</figure>

	<figure>
		<img src='https://s3-us-west-2.amazonaws.com/s.cdpn.io/2017/17_05_a_amur_leopard_14.jpg' alt='Amur leopard staring the camera with an intrigued look, as if it was preparing to strike'>
		<figcaption>one layer</figcaption>
	</figure>
</main>

<form>
	<section>
		<input type='checkbox' id='img' checked/>
		<label for='img'>Show image</label>
	</section>
</form>
!

CSS 

              
                $thumb-d: 1.5em;
$thumb-r: .5*$thumb-d;
$track-h: .375em;
$track-r: .5*$track-h;
$track-w: 17.5em;
$input-h: 1.5*$thumb-d;
$dots: .1*$track-w;
$bg: #222;
$fg: #eee;
$ll: #bbb;
$hl: #f90;
$t: .3s;

@mixin track() {
	border: none;
	width: 100%; height: $track-h;
	border-radius: $track-r;
	background: $ll;
	background: 
		radial-gradient(circle at calc(var(--pos) + #{$thumb-r}) 50%, 
			transparent $thumb-r, $ll calc(#{$thumb-r} + 1px));
	color: transparent;
}

@mixin thumb() {
	box-sizing: border-box;
	border: none;
	width: $thumb-d; height: $thumb-d;
	transform: scale(calc((.5 + .5*var(--hl))));
	border-radius: 50%;
	background: $hl;
	transition: $t
}

body {
	--a0: .5;
	--a1: .5;
	--img: 1;
	display: grid;
	grid-template-rows: max-content 1fr max-content;
	overflow-x: hidden;
	margin: 0;
	min-width: 275px;
	min-height: 100vh;
	color: $hl;
	font: 900 1em segoe script, comic sans ms, purisa, cursive;
	
	@media (max-width: 400px) { font-size: .875em }
}

form {
	display: flex;
	flex-wrap: wrap;
	width: 100%;
	background: $bg;
	color: $fg;
	font: 1.25em consolas, monospace, ubuntu mono;
	text-align: center;
	
	&:first-child { justify-content: center; }
}

section {
	padding: .5em;
	
	&:nth-child(1) { --a: var(--a0) }
	&:nth-child(2) { --a: var(--a1) }
}

[id], [for] {
	--hl: 0;
	filter: Contrast(var(--hl)) Brightness(calc(2 - var(--hl))) GrayScale(calc(1 - var(--hl)))
}

input {
	&:focus { 
		outline: solid 0 transparent;
		
		&, & ~ [for] { --hl: 1 }
	}
}

input[type='range'] {
	&::-webkit-slider-runnable-track, 
	&::-webkit-slider-thumb, & { -webkit-appearance: none }
	
	--pos: calc(var(--a)*#{$track-w});
	display: block;
	border: solid 0 transparent;
	padding: .25em 0;
	width: calc(#{$track-w} + #{$thumb-d});
	height: $input-h;
	background: transparent;
	cursor: pointer;
	
	&::-webkit-slider-runnable-track { @include track }
	
	&::-moz-range-track { @include track }
	
	&::-ms-track { @include track }
	
	&::-webkit-slider-thumb {
		margin-top: .5*($track-h - $thumb-d);
		@include thumb;
	}
	
	&::-moz-range-thumb { @include thumb }
	
	&::-ms-thumb {
		margin-top: 0;
		@include thumb
	}
	
	&::-ms-fill-lower, 
	&::-ms-fill-upper {
		background: transparent;
	}

	&::-ms-tooltip { display: none }
}

input[type='checkbox'] {
	position: absolute;
	right: 100vw;
	clip-path: inset(50%);
	
	+ label {
		display: flex;
		align-items: center;
		
		&::before {
			margin-right: .5em;
			width: $thumb-d; height: $thumb-d;
			border-radius: 5px;
			box-shadow: inset 0 0 0 2px;
			font-weight: 900;
			content: ''
		}
	}
	
	&:checked + label {
		color: $hl;
		
		&::before { content: '✓' }
	}
}

main { 
	flex: 1;
	display: flex;
	flex-wrap: wrap;
	align-items: center;
	justify-content: center
}

figure {
	position: relative;
	margin: .5vmin;
	width: $track-w + $thumb-d;
	
	&:before, &:after {
		position: absolute;
		top: 0; left: 0;
		padding: 50%;
		background: $hl;
		content: ''
	}
	
	&:nth-of-type(1) {
		&:before { opacity: var(--a0) }
		
		&:after { opacity: var(--a1) }
	}
	
	&:nth-of-type(2) {
		&:before { opacity: calc(var(--a0) + var(--a1) - var(--a0)*var(--a1)) }
		
		&:after { opacity: 0 }
	}
}

img {
	width: 100%;
	opacity: var(--img)
}

figcaption { font-size: 1.5em }
!

JS 

              
                function update(e) {
	let _t = e.target, id = _t.id, val;
	
	if(_t.type === 'range') {
		val = +(.01*_t.value).toFixed(2);
		document.querySelector(`output[for='${id}']`).textContent = val;
	}
	if(_t.type === 'checkbox') {
		val = 1*_t.checked;
	}
	
	document.body.style.setProperty(`--${id}`, val);
};

addEventListener('input', update, false);
addEventListener('change', update, false);
!
999px

Console