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CSS

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HTML 

              
                <label class="switch">
	<input id="switch" class="switch__input" type="checkbox" role="switch" data-pristine="true" />
	<span class="switch__sr">Power</span>
</label>
!

CSS 

              
                * {
	border: 0;
	box-sizing: border-box;
	margin: 0;
	padding: 0;
}
:root {
	--hue1: 223; /* primary color */
	--hue2: 123; /* “on” state */
	--hue3: 38; /* yolk */
	--hue4: 63; /* egg liquid */
	--bg: hsl(var(--hue1),90%,90%);
	--fg: hsl(var(--hue1),90%,10%);
	--primary: hsl(var(--hue1),90%,50%);
	--trans-dur: 0.4s;
	--trans-timing1: cubic-bezier(0.65, 0.05, 0.36, 1);
	--trans-timing2: cubic-bezier(0.65, -0.05, 0.36, 1.1);
	font-size: calc(30px + (60 - 30) * (100vw - 320px) / (2560 - 320));
}
body,
input {
	font: 1em/1.5 sans-serif;
}
body {
	background-color: var(--bg);
	color: var(--fg);
	display: flex;
	height: 100vh;
	perspective: 480px;
	transition:
		background-color var(--trans-dur),
		color var(--trans-dur);
}
.switch {
	animation: switchOff var(--trans-dur) var(--trans-timing1) forwards;
	border-radius: 1.5em;
	box-shadow: 0 0 0 0.125em hsla(var(--hue1),90%,50%,0);
	margin: auto;
	position: relative;
	transform-origin: 0 50%;
	transition: box-shadow 0.15s linear;
}
.switch:before,
.switch:after {
	content: "";
	display: block;
	position: absolute;
}
.switch:before {
	background-color: hsl(var(--hue1),10%,60%);
	box-shadow: 0.0625em 0 0.0625em hsla(0,0%,10%,0.8) inset;
	top: calc(50% - 0.125em);
	right: 100%;
	width: 0.5em;
	height: 0.25em;
	transition: background-color calc(var(--trans-dur) / 2) calc(var(--trans-dur) / 2) var(--trans-timing1);
}
.switch:after {
	background-image:
		radial-gradient(
			0.3em 0.3em at 25% 50%,
			hsla(var(--hue1),10%,20%,0) 30%,
			hsl(var(--hue1),10%,20%) 35% 45%,
			hsl(var(--hue1),10%,30%) 50%
		);
	border-radius: 0.25em 0.125em 0.125em 0.25em;
	box-shadow: 0 0 0.125em hsl(var(--hue1),10%,10%) inset;
	top: calc(50% - 0.25em);
	right: calc(100% + 0.5em);
	width: 1.5em;
	height: 0.5em;
}
.switch__input,
.switch__input:before,
.switch__input:after {
	display: block;
}
.switch__input {
	animation: switchOffInput var(--trans-dur) var(--trans-timing1) forwards;
	background-color: hsl(var(--hue1),10%,30%);
	border-radius: 1.5em;
	box-shadow:
		0 0 0 0.125em hsl(var(--hue1),10%,40%) inset,
		0 0 0.125em 0.375em hsl(var(--hue1),10%,25%) inset,
		0 0 0 0.375em hsl(var(--hue1),10%,55%) inset;
	outline: transparent;
	position: relative;
	width: 6em;
	height: 3em;
	-webkit-appearance: none;
	appearance: none;
	-webkit-tap-highlight-color: transparent;
}
.switch__input:before,
.switch__input:after {
	content: "";
	position: absolute;
	transition:
		background-color var(--trans-dur) var(--trans-timing1),	
		box-shadow var(--trans-dur) var(--trans-timing1),
		transform var(--trans-dur) var(--trans-timing1);
}
.switch__input:before {
	background-color: hsla(var(--hue4),90%,50%,0.15);
	box-shadow: 0.0625em 0.0625em 0 hsla(var(--hue4),0%,100%,0.15) inset;
	border-radius: 50% 40%;
	top: 0.625em;
	left: 0.5em;
	width: 2em;
	height: 1.75em;
}
.switch__input:after {
	background-color: hsl(var(--hue3),90%,50%);
	background-image:
		radial-gradient(12.5% 12.5% at 20% 25%,hsl(0,0%,100%) 45%,hsla(0,0%,100%,0) 50%),
		radial-gradient(15% 30% at 15% 50%,hsl(0,0%,100%) 45%,hsla(0,0%,100%,0) 50%);
	border-radius: 50%;
	box-shadow:
		-0.0625em 0 0 hsla(var(--hue3),10%,95%,0.9),
		-0.125em 0 0 hsl(var(--hue3),90%,45%) inset,
		0.125em 0 0.125em hsla(0,0%,10%,0.3);
	top: 1em;
	left: 1em;
	width: 1em;
	height: 1em;
	transform: rotate(45deg);
	transition-timing-function: var(--trans-timing1), var(--trans-timing1), var(--trans-timing2);
}
.switch__sr {
	overflow: hidden;
	position: absolute;
	width: 1px;
	height: 1px;
}
.switch:has([data-pristine="true"]),
.switch__input[data-pristine="true"] {
	animation: none;
}
.switch:has(:focus-visible) {
	box-shadow: 0 0 0 0.125em var(--primary);
}
.switch:has(:checked) {
	animation-name: switchOn;
}
.switch:has(:checked):before {
	background-color: hsl(var(--hue2),90%,60%);
}
.switch__input:checked {
	animation-name: switchOnInput;
}
.switch__input:checked:before {
	background-color: hsl(var(--hue4),10%,95%);
	box-shadow: -0.0625em -0.0625em 0 hsl(var(--hue4),0%,100%) inset;
	transform: translateX(3em) rotate(180deg);
}
.switch__input:checked:after {
	background-color: hsl(var(--hue3),90%,50%);
	box-shadow:
		-0.0625em -0.0625em 0 hsla(var(--hue3),10%,95%,0.6),
		-0.125em 0 0 hsl(var(--hue3),90%,45%) inset,
		0.0625em 0.0625em 0.125em hsla(0,0%,10%,0);
	transform: translateX(3em) rotate(45deg);
}

/* Dark theme */
@media (prefers-color-scheme: dark) {
	:root {
		--bg: hsl(var(--hue1),90%,10%);
		--fg: hsl(var(--hue1),90%,90%);
	}
}

/* Animations */
@keyframes switchOff {
	from, to { transform: rotateY(0); }
	50% { transform: rotateY(-15deg); }
}
@keyframes switchOffInput {
	from {
		background-color: hsl(var(--hue2),90%,30%);
		box-shadow:
			0 0 0 0.125em hsl(var(--hue2),90%,40%) inset,
			0 0 0.125em 0.375em hsl(var(--hue2),90%,25%) inset,
			0 0 0 0.375em hsl(var(--hue2),90%,55%) inset;
	}
	50% {
		background-color: hsl(var(--hue2),90%,30%);
		box-shadow:
			-0.0625em 0 0 0.125em hsl(var(--hue2),90%,40%) inset,
			0.0625em 0 0.125em 0.375em hsl(var(--hue2),90%,25%) inset,
			0.0625em 0 0 0.375em hsl(var(--hue2),90%,55%) inset;	
	}
	to {
		background-color: hsl(var(--hue1),10%,30%);
		box-shadow:
			0 0 0 0.125em hsl(var(--hue1),10%,40%) inset,
			0 0 0.125em 0.375em hsl(var(--hue1),10%,25%) inset,
			0 0 0 0.375em hsl(var(--hue1),10%,55%) inset;
	}
}
@keyframes switchOn {
	from, to { transform: rotateY(0); }
	50% { transform: rotateY(15deg); }
}
@keyframes switchOnInput {
	from {
		background-color: hsl(var(--hue1),10%,30%);
		box-shadow:
			0 0 0 0.125em hsl(var(--hue1),10%,40%) inset,
			0 0 0.125em 0.375em hsl(var(--hue1),10%,25%) inset,
			0 0 0 0.375em hsl(var(--hue1),10%,55%) inset;
	}
	50% {
		background-color: hsl(var(--hue1),10%,30%);
		box-shadow:
			0.0625em 0 0 0.125em hsl(var(--hue1),10%,40%) inset,
			-0.0625em 0 0.125em 0.375em hsl(var(--hue1),10%,25%) inset,
			-0.0625em 0 0 0.375em hsl(var(--hue1),10%,55%) inset;	
	}
	to {
		background-color: hsl(var(--hue2),90%,30%);
		box-shadow:
			0 0 0 0.125em hsl(var(--hue2),90%,40%) inset,
			0 0 0.125em 0.375em hsl(var(--hue2),90%,25%) inset,
			0 0 0 0.375em hsl(var(--hue2),90%,55%) inset;
	}
}
!

JS 

              
                // only for preventing animations from firing on load
window.addEventListener("DOMContentLoaded",() => {
	const c = new Switch("#switch");
});

class Switch {
	constructor(el) {
		this.el = document.querySelector(el);
		this.el?.addEventListener("change",this.removePristine);
	}
	removePristine() {
		this.removeAttribute("data-pristine");
	}
}
!
999px

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