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CSS

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HTML 

              
                <main>
	<div class="clock" role="img" aria-label="Analog clock">
		<div class="clock__inner-frame"></div>
		<div class="clock__ticks">
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
			<div class="clock__tick"></div>
		</div>
		<div class="clock__digits">
			<div class="clock__digit">1</div>
			<div class="clock__digit">2</div>
			<div class="clock__digit">3</div>
			<div class="clock__digit">4</div>
			<div class="clock__digit">5</div>
			<div class="clock__digit">6</div>
			<div class="clock__digit">7</div>
			<div class="clock__digit">8</div>
			<div class="clock__digit">9</div>
			<div class="clock__digit">10</div>
			<div class="clock__digit">11</div>
			<div class="clock__digit">12</div>
		</div>
		<div class="clock__text">
			<em>Radio Controlled</em>
		</div>
		<div class="clock__hands">
			<div class="clock__hand clock__hand--hr"></div>
			<div class="clock__hand clock__hand--min"></div>
			<div class="clock__hand clock__hand--sec"></div>
		</div>
	</div>
</main>
!

CSS 

              
                @mixin handRotate($iteration,$iterations,$maxPct: 100%)
	$frac: $iteration / $iterations
	#{($maxPct * $frac)}
		transform: rotate(-360deg * (($iterations - 1) / $iterations) * $iteration)

$hue: 223

*
	border: 0
	box-sizing: border-box
	margin: 0
	padding: 0

\:root
	--bg: #{hsl($hue,10%,90%)}
	--fg: #{hsl($hue,10%,10%)}
	font-size: calc(16px + (24 - 16) * (100vw - 320px) / (1280 - 320))

body
	background: var(--bg)
	color: var(--fg)
	font: 1em/1.5 -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", Helvetica, sans-serif
	height: 100vh
	display: grid
	place-items: center
main
	padding: 1.5em 0

.clock
	background: radial-gradient(100% 100% at 50% 10%,hsl($hue,10%,50%),hsl($hue,10%,10%) 50%)
	border-radius: 50%
	box-shadow: 0 0.5em 1em hsla(0,0%,0%,0.5)
	position: relative
	width: 15em
	height: 15em
	&__inner-frame,
	&__ticks,
	&__tick,
	&__digits,
	&__digit,
	&__text,
	&__hands,
	&__hand,
	&__hand-trail
		position: absolute
	&__inner-frame,
	&__ticks,
	&__digits,
	&__hands
		border-radius: inherit
	&__inner-frame
		background: linear-gradient(hsl($hue,10%,60%),hsl($hue,10%,80%))
		box-shadow: 0 0.1em 0 hsl(0,0%,80%) inset
		top: 1em
		left: 1em
		width: 13em
		height: 13em	
	&__ticks
		background: linear-gradient(hsl($hue,10%,90%),hsl($hue,10%,100%))
		box-shadow: 0 0.5em 0.5em 0.75em hsla(0,0%,0%,0.2) inset, 0 0 0 0.15em hsl($hue,10%,10%)
		top: 1.5em
		left: 1.5em
		width: 12em
		height: 12em
	&__tick,
	&__hand
		background: currentColor
	&__tick
		bottom: 50%
		left: calc(50% - 0.025em)
		width: 0.05em
		min-width: 1px
		height: 0.25em
		transform-origin: 50% 100%
		&:nth-child(5n + 1)
			left: calc(50% - 0.05em)
			width: 0.1em
			min-width: 2px
			height: 0.5em	
		$ticks: 60
		$transY: -5.5em
		@for $t from 1 through $ticks
			$transYAdj: $transY
			@if $t % 5 == 1
				$transYAdj: $transY + 0.25
			&:nth-child(#{$t})
				transform: rotate(360deg/$ticks * ($t - 1)) translateY($transYAdj)
	&__digits
		top: 2.5em
		left: 2.5em
		width: 10em
		height: 10em
	&__digit
		font-size: 1.5em
		line-height: 1
		letter-spacing: -0.05em
		text-align: center
		top: calc(50% - 0.75rem)
		left: calc(50% - 1.25rem)
		width: 2.5rem
		height: 1.5rem
		@for $t from 1 through 12
			&:nth-child(#{$t})
				transform: rotate(30deg * $t) translateY(-4.25rem) rotate(-30deg * $t)
	&__text
		font-size: 0.4em
		text-align: center
		text-transform: uppercase
		top: 65%
		left: 0
		width: 100%
	&__hands
		filter: drop-shadow(0 0.5em 0.1em hsla(0,0%,0%,0.3))
		top: 2.5em
		left: 2.5em
		width: 10em
		height: 10em
	&__hand
		$timing: cubic-bezier(0.8,0,0.2,1)
		&--hr
			animation: hrHand 86400s $timing infinite
			border-radius: 0 0 0.2em 0.2em
			bottom: calc(50% - 0.2em)
			left: calc(50% - 0.2em)
			width: 0.4em
			height: 3.25em
			transform-origin: 50% calc(100% - 0.2em)
		&--min
			animation: longHand 3600s $timing infinite
			border-radius: 0 0 0.15em 0.15em
			bottom: calc(50% - 0.15em)
			left: calc(50% - 0.15em)
			width: 0.3em
			height: 5em
			transform-origin: 50% calc(100% - 0.15em)
		&--sec
			animation: longHand 60s $timing infinite
			bottom: calc(50% - 1.5em)
			left: calc(50% - 0.1em)
			width: 0.2em
			height: 6.5em
			transform-origin: 50% calc(100% - 1.5em)
			&:before
				background-color: inherit
				border-radius: 50%
				content: ""
				display: block
				position: absolute
				bottom: 1.3em
				left: calc(50% - 0.2em)
				width: 0.4em
				height: 0.4em

/* Dark theme */
@media (prefers-color-scheme: dark)
	\:root
		--bg: #{hsl($hue,10%,20%)}
		--fg: #{hsl($hue,10%,90%)}
	.clock
		background: radial-gradient(100% 100% at 50% 10%,hsl($hue,10%,100%),hsl($hue,10%,60%) 50%)
		&__inner-frame
			background: linear-gradient(hsl($hue,10%,30%),hsl($hue,10%,50%))
			box-shadow: 0 0.1em 0 hsl(0,0%,60%) inset
		&__ticks
			background: linear-gradient(hsl($hue,10%,10%),hsl($hue,10%,20%))

/* Animations */
@keyframes hrHand
	@for $h from 0 through 24
		@include handRotate($h,12,50%)
@keyframes longHand
	@for $l from 0 through 60
		@include handRotate($l,60)
!

JS 

              
                window.addEventListener("DOMContentLoaded",() => {
	const clock = new ReverseClock(".clock");
});

class ReverseClock {
	constructor(qs,h,m,s,ms) {
		const el = document.querySelector(qs);
		const msInSec = 1000;
		const msInMin = msInSec * 60;
		const msInHr = msInMin * 60;
		const msInDay = msInHr * 24;
		const date = new Date();

		let time = (h === undefined ? date.getHours() : h) * msInHr;
		time += (m === undefined ? date.getMinutes() : m) * msInMin;
		time += (s === undefined ? date.getSeconds() : s) * msInSec;
		time += ms === undefined ? date.getMilliseconds() : ms;

		if (el) {
			const handCl = ".clock__hand";
			const hr = el.querySelector(`${handCl}--hr`);
			const min = el.querySelector(`${handCl}--min`);
			const sec = el.querySelector(`${handCl}--sec`);

			if (hr) {
				const hrDelay = (msInDay * ((time % msInDay) / msInDay)) / msInSec;
				hr.style.animationDelay = `${-hrDelay}s`;
			}
			if (min) {
				const minDelay = (msInHr * ((time % msInHr) / msInHr)) / msInSec;
				min.style.animationDelay = `${-minDelay}s`;
			}
			if (sec) {
				const secDelay = (msInMin * ((time % msInMin) / msInMin)) / msInSec;
				sec.style.animationDelay = `${-secDelay}s`;
			}
		}
	}
}
!
999px

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