<div id="rs" class="rs rs--pristine">
	<div class="rs__range-wrap">
		<input class="rs__range" type="range" data-range>
	</div>
	<div class="rs__rings">
		<button class="rs__handle" type="button" data-handle>
			<span class="rs__handle-value" data-value>0</span>
		</button>
		<div class="rs__ring"></div>
		<div class="rs__ring"></div>
		<div class="rs__ring"></div>
		<div class="rs__ring"></div>
		<div class="rs__ring"></div>
		<div class="rs__ring"></div>
		<div class="rs__ring"></div>
	</div>
</div>

* {
	border: 0;
	box-sizing: border-box;
	margin: 0;
	padding: 0;
}
:root {
	--hue: 223;
	--bg: hsl(var(--hue),10%,90%);
	--fg: hsl(var(--hue),10%,10%);
	--primary: hsl(var(--hue),90%,55%);
	--trans-dur: 0.3s;
	font-size: calc(16px + (24 - 16) * (100vw - 320px) / (1280 - 320));
}
body,
button,
input {
	font: 1em/1.5 "Source Code Pro", monospace;
}
body {
	background-color: var(--bg);
	color: var(--fg);
	height: 100vh;
	display: grid;
	overflow: hidden;
	place-items: center;
	transition:
		background-color var(--trans-dur),
		color var(--trans-dur);
}

.rs,
.rs__rings {
	position: relative;
}
.rs {
	--rel-value: 0;
	--range-units: 1;
	transition: transform 0.3s ease-in-out;
}
.rs__range-wrap,
.rs__rings {
	transform: rotateX(30deg) rotateY(30deg);
	transform-style: preserve-3d;
}
.rs__range:focus,
.rs__handle:focus {
	outline: transparent;
}
.rs__range-wrap {
	display: none;
	position: absolute;
	inset: 0;
	z-index: 1;
}
.rs__range {
	background-color: transparent;
	position: absolute;
	top: 50%;
	left: 50%;
	width: 24em;
	height: 12em;
	transform: translate(-50%,-50%) rotateX(90deg) rotateZ(90deg);
	-webkit-appearance: none;
	appearance: none;
}
.rs__range::-webkit-slider-thumb {
	background-color: transparent;
	border: 0;
	width: 12em;
	height: 8em;
	transform: skewY(30deg);
	-webkit-appearance: none;
	appearance: none;
}
.rs__range::-moz-range-thumb {
	background-color: transparent;
	border: 0;
	width: 12em;
	height: 8em;
	transform: skewY(30deg);
}
.rs__rings {
	z-index: 0;
}
.rs__handle,
.rs__ring {
	border-radius: 2em;
	box-shadow: 0 0 0 0.25em inset;
}
.rs__handle {
	background-color: transparent;
	color: var(--fg);
	position: relative;
	width: 8em;
	height: 8em;
	transition:
		box-shadow var(--trans-dur),
		color var(--trans-dur),
		transform var(--trans-dur) linear;
	-webkit-appearance: none;
	appearance: none;
	-webkit-tap-highlight-color: transparent;
	user-select: none;
	-webkit-user-select: none;
	-moz-user-select: none;
}
.rs__handle:before {
	animation: handleBlur var(--trans-dur) ease-in-out;
	border-radius: 50%;
	box-shadow: 0 0 0 0 inset;
	content: "";
	display: block;
	opacity: 0.1;
	position: absolute;
	top: -25%;
	left: -25%;
	width: 150%;
	height: 150%;
}
.rs__handle:focus {
	color: var(--primary);
}
.rs__handle-value {
	font-size: 3em;
	font-weight: 300;
	line-height: 1;
}
.rs__ring {
	position: absolute;
	inset: 0;
	opacity: 0.1;
	pointer-events: none;
	visibility: hidden;
	transition:
		transform var(--trans-dur) linear,
		visibility var(--trans-dur) steps(1);
}
.rs--pristine .rs__handle:before {
	animation: none;
}
.rs--active .rs__handle {
	pointer-events: none;
	transform: translateZ(calc(-6em + (var(--rel-value) / var(--range-units) * 12em)));
}
.rs--active .rs__handle:before {
	animation: handleFocus 0.6s ease-in-out;
	box-shadow: 0 0 0 6em inset;
	transform: scale(0.4);
}
.rs--active .rs__range-wrap { display: block; }

.rs--active .rs__ring {
	visibility: visible;
	transition-duration: var(--trans-dur), 0s;
}

.rs--active .rs__ring:nth-of-type(1) { transform: translateZ(6em); }
.rs--active .rs__ring:nth-of-type(2) { transform: translateZ(4em); }
.rs--active .rs__ring:nth-of-type(3) { transform: translateZ(2em); }
.rs--active .rs__ring:nth-of-type(4) { transform: translateZ(0); }
.rs--active .rs__ring:nth-of-type(5) { transform: translateZ(-2em); }
.rs--active .rs__ring:nth-of-type(6) { transform: translateZ(-4em); }
.rs--active .rs__ring:nth-of-type(7) { transform: translateZ(-6em); }

/* Dark theme */
@media (prefers-color-scheme: dark) {
	:root {
		--bg: hsl(var(--hue),10%,10%);
		--fg: hsl(var(--hue),10%,90%);
		--primary: hsl(var(--hue),90%,65%);
	}
}

/* Animations */
@keyframes handleBlur {
	from {
		box-shadow: 0 0 0 6em inset;
		transform: scale(0.4);
	}
	to {
		box-shadow: 0 0 0 0.1em inset;
		transform: scale(1);
	}
}
@keyframes handleFocus {
	from { transform: scale(0); }
	33% { transform: scale(0.5); }
	67% { transform: scale(0.35); }
	to { transform: scale(0.4); }
}

window.addEventListener("DOMContentLoaded",() => {
	const slider = new _3DRangeSlider("#rs");
});

class _3DRangeSlider {
	constructor(qs) {
		this.el = document.querySelector(qs);
		this.handle = this.el?.querySelector("[data-handle]");
		this.range = this.el?.querySelector("[data-range]");
		this.value = 3;
		this.min = 0;
		this.max = 6;
		this.step = 1;
		this.active = false;
		this.rangeFocusTimeout = null;

		this.init();
	}
	init() {
		if (this.el) {
			this.handle?.addEventListener("click",this.expand.bind(this));

			if (this.range) {
				this.range.value = this.value;
				this.range.min = this.min;
				this.range.max = this.max;
				this.range.step = this.step;

				this.range.addEventListener("input",this.adjust.bind(this));
				document.addEventListener("click",this.collapse.bind(this));
				document.addEventListener("keydown",this.collapse.bind(this));
			}

			this.updateDisplay();
		}
	}
	expand() {
		this.active = true;
		this.handle.blur();
		this.handle.disabled = this.active;

		this.el.classList.remove("rs--pristine");
		this.el.classList.add("rs--active");

		clearTimeout(this.rangeFocusTimeout);
		this.rangeFocusTimeout = setTimeout(() => this.range.focus(),1);
	}
	collapse(e) {
		if (e.key === "Escape" || (!e.key && e.target === document.body)) {
			this.active = false;
			this.handle.disabled = this.active;
			this.el.classList.remove("rs--active");
		}
	}
	adjust(e) {
		this.value = e.target.value;

		this.updateDisplay();
	}
	updateDisplay() {
		if (this.el) {
			// CSS variables
			this.el.style.setProperty("--rel-value",this.value - this.min);
			this.el.style.setProperty("--range-units",this.max - this.min);

			// displayed value
			const value = this.el.querySelector("[data-value]");

			if (value)
				value.textContent = this.value;
		}
	}
}