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	<input id='r' type='range' min='10' value='50' max='80'/>
	<label for='r'>we have a <output for='r'>50</output> scoop radius</label>

<div class='box'>
	<mask id='m' fill='#fff'>
		<rect width='100%' height='100%'/>
		<circle id='c' r='15%' fill='#000'/>
		<use xlink:href='#c' x='100%'/>
		<use xlink:href='#c' y='100%'/>
		<use xlink:href='#c' x='100%' y='100%'/>
	<h3>The Amur Leopard</h3>
	<p>The Amur leopard has some very distinguishing features. The hairs of its summer pelt are 2.5 cm long but in winter they are replaced by 7 cm long ones.</p>
	<p>Apart from its long winter coat, which is a light colour in the winter, and more reddish-yellow in the summer, the Amur leopard is easily told apart from other leopard subspecies by its widely spaced rosettes with thick borders. It also has longer legs, probably an adaptation for walking through snow.</p>
	<em>from <a href=''></a></em>


                $theme-dark: #262626;
$theme-light: invert($theme-dark);
$theme-orange: #f90;
$theme-tomato: #b53;
$theme-purple: #95a;

.box {
	position: relative;
	margin: .75em auto 0;
	padding: var(--r);
	width: calc(100% - 2*var(--r) - 1em);
	max-width: 47em; min-height: 15em;
	background: rgba($theme-purple, .85);
	color: #fff;
	font: 1em trebuchet ms, verdana, sans-serif;
	mask: url(#m);

svg {
	position: absolute;
	width: 100%; height: 100%


//* slider variables */
$track-w: 90vw;
$track-h: .25em;
$thumb-d: 1.5em;

//* slider mixins */
@mixin track() {
	box-sizing: border-box;
	border: none;
	width: 100%; height: $track-h;
	border-radius: $track-h;
	background: $theme-light

@mixin thumb() {
	box-sizing: border-box;
	border: none;
	width: $thumb-d; height: $thumb-d;
	border-radius: 50%;
	background: currentcolor

* {
	margin: 0;
	color: inherit;
	font: inherit

html {
	$over-c: rgba($theme-light, .5);
	overflow-x: hidden;
	min-width: 10em; height: 100%;
		linear-gradient($over-c, $over-c), 
		url( 0 0/ cover;
	font: 1em/ 1.25 trebuchet ms, verdana, arial, sans-serif

h3 {
	font: 700 2em/ 1.5 kalam, cursive;
	text-align: center

p { padding: .75em 0 }

em {
	display: block;
	font-style: italic;
	text-align: right

a { color: lighten($theme-orange, 15%) }

form {
	padding: .75em;
	background: $theme-dark;
	color: $theme-light;
	text-align: center

[type='range'] {
	&, &::-webkit-slider-thumb {
		-webkit-appearance: none
	display: block;
	margin: 0 auto 1em;
	padding: 0;
	width: $track-w; height: $thumb-d;
	background: transparent;
	cursor: pointer;
	&::-webkit-slider-runnable-track {
		@include track
	&::-moz-range-track { @include track }
	&::-ms-track { @include track }
	&::-webkit-slider-thumb {
		margin-top: .5*($track-h - $thumb-d);
		@include thumb
	&::-moz-range-thumb { @include thumb }
	&::-ms-thumb {
		margin-top: 0;
		@include thumb
	&::-ms-tooltip { display: none }
	&:focus {
		outline: solid 1px transparent;
		color: $theme-orange;
		+ label output { color: $theme-orange }

label { display: block }

output { font: 1.125em/ 2 consolas, monaco, monospace }

output:after { content: 'px' }


                const _R = document.getElementById('r'), 
			_C = document.getElementById('c'), 
			_O = _R.nextElementSibling.querySelector('output');

let v;

function update() {
	if(v !== +_R.value) {`--r`, `${_O.value = v = +_R.value}px`)
		_C.setAttribute('r', `${v}px`)


_R.addEventListener('change', update, false);
_R.addEventListener('input', update, false);