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HTML

              
                <div class="head">
	<h1>Engine simulator</h1>
</div>

<div class="dashboard">
	<div class="meter meter--rpm meter--big-label"></div>
	<div class="meter meter--gear"><div>1</div></div>
	<div class="meter meter--speed"></div>
</div>

<div class="help">
	Accelerate / brake : up/down arrow<br>
	Gears +/- : left/right arrows<br>
</div>

<button class="btn-volume active">♩</button>

<div class="loader active">Loading...</div>


              
            
!

CSS

              
                $meter-bg-color: white;

$ring-size: 3.5%;
$ring-color: #333;

$grad-font-size: 1.25rem;
$grad-font-size-big: 2rem;
$grad-color: #555;

/*
$meter-bg-color: rgb(32,32,32);
$ring-color: #eee;
$grad-color: #9affff;
*/

$tick-color: $grad-color;

$needle-width: 5px;
$needle-side-width: 3px;
$needle-height: 140px;
$needle-color: #e30;
$needle-shading: 5%;

$needle-axle-bg-color: $ring-color;
$needle-axle-color: #eee;
$needle-axle-size: 15%;
$needle-axle-size-big: 37.5%;

$label-color: $grad-color;


@mixin shadow ($level: 2, $inset: false) {

   @if $inset {

		 @if $level == 1 {
			 box-shadow: inset 0 1px 3px rgba(0,0,0,0.12), inset 0 1px 2px rgba(0,0,0,0.24);
		 } @else if $level == 2 {
			 box-shadow: inset 0 3px 6px rgba(0,0,0,0.16), inset 0 3px 6px rgba(0,0,0,0.23);
		 } @else if $level == 3 {
			 box-shadow: inset 0 10px 20px rgba(0,0,0,0.19), inset 0 6px 6px rgba(0,0,0,0.23);
		 } @else if $level == 4 {
			 box-shadow: inset 0 14px 28px rgba(0,0,0,0.25), inset 0 10px 10px rgba(0,0,0,0.22);
		 } @else if $level == 5 {
			 box-shadow: inset 0 19px 38px rgba(0,0,0,0.30), inset 0 15px 12px rgba(0,0,0,0.22);
		 }

	}	@else {
		@if $level == 1 {
			box-shadow: 0 1px 3px rgba(0,0,0,0.12), 0 1px 2px rgba(0,0,0,0.24);
		} @else if $level == 2 {
			box-shadow: 0 3px 6px rgba(0,0,0,0.16), 0 3px 6px rgba(0,0,0,0.23);
		} @else if $level == 3 {
			box-shadow: 0 10px 20px rgba(0,0,0,0.19), 0 6px 6px rgba(0,0,0,0.23);
		} @else if $level == 4 {
			box-shadow: 0 14px 28px rgba(0,0,0,0.25), 0 10px 10px rgba(0,0,0,0.22);
		} @else if $level == 5 {
			box-shadow: 0 19px 38px rgba(0,0,0,0.30), 0 15px 12px rgba(0,0,0,0.22);
		}
	}
}




//@import url(https://fonts.googleapis.com/css?family=Coda:400,800);
@import url(https://fonts.googleapis.com/css?family=Coda:400|Roboto+Mono:400,400italic);

* {
	box-sizing: border-box;
//	transition: all 0.2s ease-in-out;
}

.dashboard {
	display: inline-block;
	padding: 2rem;
//	background: #ddd;
	font-family: 'Coda', cursive;
}

.meter {
	display: inline-block;
	position: relative;
	width: 20rem;
	height: 20rem;
	background-color: $meter-bg-color;
	border-radius: 50%;
//	border: 4px solid black;
	margin: 0 0.5rem;
	@include shadow(2, true);
	
	&:before {
		content: "";
		display: block;
		position: absolute;
		width: 100% + $ring-size * 2;
		left: -$ring-size;
		top: -$ring-size;
		bottom: -$ring-size;
		border-radius: 50%;
		background: $ring-color;
		z-index: -1;
		@include shadow(3);
	}
}

.label {
	position: absolute;
	left: 50%;
	transform: translate3d(-50%, -50%, 0);
	text-align: center;
	color: $label-color;

	&.label-value {
		color: $needle-axle-color;
	}
	
	span {
		text-transform: uppercase;
	}
}

.label-unit {
	top: 82.5%;
	
	div {
		
		font-size: 1rem;

		.meter--big-label & {
			font-size: 0;
		}
	}
}

.label-value {
	top: 50%;
	line-height: 1.25;
	
	div, span {
		font-size: 0;

		.meter--big-label & {
			font-size: 2.5rem;
		}
	}
	
	div {
		font-family: 'Roboto Mono', monospace;
		font-style: italic;
	}
	
	span {
		.meter--big-label & {
			font-size: 1rem;
		}
	}
	
	span {
		display: block;
		position: absolute;
		left: 50%;
		transform: translate3d(-50%, 0, 0);
	}
}

.needle,
.needle-axle {
	
}

.needle {
	position: absolute;
	top: 50%;
	left: 50%;
	display: block;
	width: $needle-width;
	height: $needle-height;
	transform: translate3d(-50%, 0, 0);
	transform-origin: 50% 0;
	background-color: $needle-color;
	@include shadow(1);

	&:before,
	&:after {
		display: block;
		position: absolute;
		content: "";
		width: 0;
		height: 0;
		border-style: solid;
	}
	
	&:before {
		left: -$needle-side-width;
		border-width: 0 $needle-side-width $needle-height 0;
		border-color: transparent lighten($needle-color, $needle-shading * 2) transparent transparent;
	}
	
	&:after {
		right: -$needle-side-width;
		border-width: $needle-height $needle-side-width 0 0;
		border-color: darken($needle-color, $needle-shading) transparent transparent transparent;
	}
}

.needle-axle {
	position: absolute;
	top: 50%;
	left: 50%;
	display: block;
	width: $needle-axle-size;
	height: $needle-axle-size;
	transform: translate3d(-50%, -50%, 0);
	border-radius: 50%;
	background-color: $needle-axle-bg-color;
	color: $needle-axle-color;
	@include shadow(2);
	cursor: pointer;
	
	&:hover {
		background-color: darken($needle-axle-bg-color, 20%);
	}
	
	.meter--big-label & {
		width: $needle-axle-size-big;
		height: $needle-axle-size-big;
	}
}

.grad {
	position: absolute;
	display: inline-block;
	font-size: $grad-font-size;
	line-height: 1;
	color: $grad-color;
	transform: translate3d(-50%, -50%, 0);
	font-weight: bold;
	
	&.redzone {
		color: $needle-color;
	}

	.meter--rpm & {
		font-size: $grad-font-size-big;
	}
}

.grad-tick,
.grad-tick--half,
.grad-tick--quarter {

	&.redzone {
		background-color: $needle-color;
	}
}


.grad-tick {
	position: absolute;
	display: block;
	width: 4px;
	height: 0.75em;
	transform-origin: 50% 0;
	background-color: $tick-color;
}

.grad-tick--half {
	width: 2px;
	height: 0.5em;
}

.grad-tick--quarter {
	width: 2px;
	height: 0.25em;
}


// Gear-meter

.meter--gear {
	width: 5rem;
	height: 5rem;
	margin: 0;
	margin-left: -2rem;
	margin-right: -2rem;
	@include shadow(2, true);

	&:before {
		width: 100% + $ring-size * 4 * 2;
		height: 100% + $ring-size * 4 * 2;
		left: -$ring-size * 4;
		top: -$ring-size * 4;
		bottom: -$ring-size * 4;
	}

	div {
		font-size: 2.5rem;
		text-align: center;
		line-height: 5rem;
		font-family: 'Roboto Mono', monospace;
		font-style: italic;
		font-weight: bold;
		color: $grad-color;

		&.redzone {
			color: $needle-color;
		}
	}

}


// UI

.loader {
	display: none;
	position: absolute;
	top: 50%;
	left: 50%;
	transform: translate3d(-50%, -50%, 0);
	background: tomato;
	color: white;
	padding: 2rem;
	text-transform: uppercase;
	
	&.active {
		display: inline-block;
	}
}

.btn-volume {
	position: fixed;
	top: 0.5rem;
	right: 0.5rem;

	width: 2.5rem;
	height: 2.53rem;
	line-height: 2rem;
	border-radius: 50%;
	background: transparent;
	color: gray;
	border: 4px solid;
	font-size: 1.5rem;
	font-weight: bold;
	
	&.active {
		color: tomato;
		border-color: tomato;
	}
}

// DEMO STYLES

body {
	text-align: center;
	// Carbon fiber FTW
/*	background:
		linear-gradient(27deg, #151515 5px, transparent 5px) 0 5px,
		linear-gradient(207deg, #151515 5px, transparent 5px) 10px 0px,
		linear-gradient(27deg, #222 5px, transparent 5px) 0px 10px,
		linear-gradient(207deg, #222 5px, transparent 5px) 10px 5px,
		linear-gradient(90deg, #1b1b1b 10px, transparent 10px),
		linear-gradient(#1d1d1d 25%, #1a1a1a 25%, #1a1a1a 50%, transparent 50%, transparent 75%, #242424 75%, #242424);
		background-color: #131313;
		background-size: 20px 20px;
*/
}

.head,
.help {
	padding: 1rem;
	color: #888;
	text-align: center;
	font-style: italic;
}

.help {
	border-top: 1px solid;
}

.head {
	border-bottom: 1px solid;
}

h1 {
	margin: 0;
//	font-family: 'Roboto Mono', monospace;
	font-weight: normal;
	text-transform: uppercase;
}
              
            
!

JS

              
                let motorSamplePath = 'https://freesound.org/data/previews/127/127980_2335231-lq.ogg';

// METER

let Meter = function Meter($elm, config) {
	
	// DOM
	let $needle, $value;
	
	// Others
	
	let steps = (config.valueMax - config.valueMin) / config.valueStep,
			angleStep = (config.angleMax - config.angleMin) / steps;
	
	let margin = 10; // in %
	let angle = 0; // in degrees
	
	let value2angle = function(value) {
		let angle = ((value / (config.valueMax - config.valueMin)) * (config.angleMax - config.angleMin) + config.angleMin);

		return angle;
	};
	
	this.setValue = function(v) {
		$needle.style.transform = "translate3d(-50%, 0, 0) rotate(" + Math.round(value2angle(v)) + "deg)";
		$value.innerHTML = config.needleFormat(v);
	};
	
	let switchLabel = function(e) {
		e.target.closest(".meter").classList.toggle('meter--big-label');
	};
	
	let makeElement = function(parent, className, innerHtml, style) {

		let	e = document.createElement('div');
		e.className = className;

		if (innerHtml) {
			e.innerHTML = innerHtml;
		}

		if (style) {
			for (var prop in style) {
				e.style[prop] = style[prop];
			}
		}

		parent.appendChild(e);
		
		return e;
	};

	// Label unit
	makeElement($elm, "label label-unit", config.valueUnit);

	for (let n=0; n < steps+1; n++) {
		let value = config.valueMin + n * config.valueStep;
		angle = config.angleMin + n * angleStep;
		
		// Graduation numbers
		
		// Red zone
		let redzoneClass = "";
		if (value > config.valueRed) {
			redzoneClass = " redzone";
		}
		
		makeElement($elm, "grad grad--" + n + redzoneClass, config.labelFormat(value), {
			left: (50 - (50 - margin) * Math.sin(angle * (Math.PI / 180))) + "%",
			top: (50 + (50 - margin) * Math.cos(angle * (Math.PI / 180))) + "%"
		});	

		// Tick
		makeElement($elm, "grad-tick grad-tick--" + n + redzoneClass, "", {
			left: (50 - 50 * Math.sin(angle * (Math.PI / 180))) + "%",
			top: (50 + 50 * Math.cos(angle * (Math.PI / 180))) + "%",
			transform: "translate3d(-50%, 0, 0) rotate(" + (angle + 180) + "deg)"
		});

		// Half ticks
		angle += angleStep / 2;
		
		if (angle < config.angleMax) {
			makeElement($elm, "grad-tick grad-tick--half grad-tick--" + n + redzoneClass, "", {
				left: (50 - 50 * Math.sin(angle * (Math.PI / 180))) + "%",
				top: (50 + 50 * Math.cos(angle * (Math.PI / 180))) + "%",
				transform: "translate3d(-50%, 0, 0) rotate(" + (angle + 180) + "deg)"
			});
		}

		// Quarter ticks
		angle += angleStep / 4;
		
		if (angle < config.angleMax) {
			makeElement($elm, "grad-tick grad-tick--quarter grad-tick--" + n + redzoneClass, "", {
				left: (50 - 50 * Math.sin(angle * (Math.PI / 180))) + "%",
				top: (50 + 50 * Math.cos(angle * (Math.PI / 180))) + "%",
				transform: "translate3d(-50%, 0, 0) rotate(" + (angle + 180) + "deg)"
			});
		}

		angle -= angleStep / 2;
		
		if (angle < config.angleMax) {
			makeElement($elm, "grad-tick grad-tick--quarter grad-tick--" + n + redzoneClass, "", {
				left: (50 - 50 * Math.sin(angle * (Math.PI / 180))) + "%",
				top: (50 + 50 * Math.cos(angle * (Math.PI / 180))) + "%",
				transform: "translate3d(-50%, 0, 0) rotate(" + (angle + 180) + "deg)"
			});
		}
	}
	
	// NEEDLE
	
	angle = value2angle(config.value);
	
	$needle = makeElement($elm, "needle", "", {
		transform: "translate3d(-50%, 0, 0) rotate(" + angle + "deg)"
	});
	
	let $axle = makeElement($elm, "needle-axle").addEventListener("click", switchLabel);
	makeElement($elm, "label label-value", "<div>" + config.labelFormat(config.value) + "</div>" + "<span>" + config.labelUnit + "</span>").addEventListener("click", switchLabel);
	
	$value = $elm.querySelector(".label-value div");
};


// DOM LOADED FIESTA

document.addEventListener("DOMContentLoaded",	function() {	
	
	let rpmMeter = new Meter(document.querySelector(".meter--rpm"), {
		value: 6.3,
		valueMin: 0,
		valueMax: 8000,
		valueStep: 1000,
		valueUnit: "<div>RPM</div><span>x1000</span>",
		angleMin: 30,
		angleMax: 330,
		labelUnit: "RPM",
		labelFormat: function(v) { return Math.round(v / 1000); },
		needleFormat: function(v) { return Math.round(v / 100) * 100; },
		valueRed: 6500
	});

	let speedMeter = new Meter(document.querySelector(".meter--speed"), {
		value: 203,
		valueMin: 0,
		valueMax: 220,
		valueStep: 20,
		valueUnit: "<span>Speed</span><div>Km/h</div>",
		angleMin: 30,
		angleMax: 330,
		labelUnit: "Km/h",
		labelFormat: function(v) { return Math.round(v); },
		needleFormat: function(v) { return Math.round(v); }
	});

	let gearMeter = document.querySelector('.meter--gear div');
	
	// USER INPUTS
	
	document.onkeydown = keyDown;
	document.onkeyup = keyUp;

	function keyDown(e) {

		e = e || window.event;

		if (e.keyCode == '38') { 			// up arrow
			isAccelerating = true;
		}
		else if (e.keyCode == '40') { // down arrow
			isBraking = true;
		}
		else if (e.keyCode == '37') { // left arrow
		}
		else if (e.keyCode == '39') { // right arrow
		}

	}	

	function keyUp(e) {

		e = e || window.event;

		if (e.keyCode == '38') {			// up arrow
			isAccelerating = false;
		}
		else if (e.keyCode == '40') { // down arrow
			isBraking = false;
		}
		else if (e.keyCode == '37') { // left arrow
			gearDown();
		}
		else if (e.keyCode == '39') { // right arrow
			gearUp();
		}

	}	
	
	function gearUp() {
		if (gear < gears.length - 1) {
			gear++;
			gearMeter.innerHTML = gear;
		}
	}

	function gearDown() {
		if (gear > 1) {
			gear--;
			gearMeter.innerHTML = gear;
		}
	}

	
	// VEHICLE CONFIG

	let 
			mass = 1000,
			cx = 0.28,
			gears = [0, 0.4, 0.7, 1.0, 1.3, 1.5, 1.68],
			transmitionRatio = 0.17,
			transmitionLoss = 0.15,
			wheelDiameter = 0.5,
			brakeTorqueMax = 300,

			gear = 1,
			speed = 10,	// in km/h
			overallRatio,
			wheelRpm,
			wheelTorque,
			brakeTorque,
			resistance,
			acceleration;
	
	// MOTOR CONFIG
	
	let 
			rpmIdle = 1200,
			rpmMax = 8000,
			rpmRedzone = 6500,
			torqueMin = 20, // in m.kg
			torqueMax = 45, // in m.kg

			torque,
			rpm = 0,
			isAccelerating = false,
			isBraking = false;
	

	// Helper functions
	
	let torqueByRpm = function(rpm) {
		let torque = torqueMin + (rpm / rpmMax) * (torqueMax - torqueMin);
		return torque;
	};
	
	function kmh2ms(speed) {	// Km/h to m/s
		return speed / 3.6;
	}
	
	// Physics 101
	/* 
	 * P = C w
	 * P(hp) = C(m.kg) w(rpm) / 716
	 *
	 * F = m.a
	 * Force(newton) = mass(kg) * acceleration (m/s)
	 *
	 * a = Cr / (r.m)
	 * acceleration (m/s) = torqueWheel (m.kg) / (wheelRadius (m) * mass (kg))
	 */

	let lastTime = new Date().getTime(),
			nowTime,
			delta;
	
	
	// MAIN LOOP
	
	(function loop(){
		window.requestAnimationFrame(loop);

		// Delta time
		nowTime = new Date().getTime();
		delta = (nowTime - lastTime) / 1000; // in seconds
		lastTime = nowTime;
		
		let oldSpeed = speed,
				oldRpm = rpm;
		
		// Torque
		
		if (isAccelerating && rpm < rpmMax) {	// Gas!
			torque = torqueByRpm(rpm);

		} else {
			torque = -(rpm * rpm / 1000000);
		}
		
		if (isBraking) {	// Ooops...
			brakeTorque = brakeTorqueMax;
		} else {
			brakeTorque = 0;
		} 
		
		
		overallRatio = transmitionRatio * gears[gear];
		wheelTorque = torque / overallRatio - brakeTorque;
		
		acceleration = 20 * wheelTorque / (wheelDiameter * mass / 2);
		resistance = 0.5 * 1.2 * cx * kmh2ms(speed)^2;

		// Speed
		
		speed += (acceleration - resistance) * delta;
		
		
		if (speed < 0) { speed = 0; }
		
		wheelRpm = speed / (60 * (Math.PI * wheelDiameter / 1000));
		rpm = speed / (60 * transmitionRatio * gears[gear] * (Math.PI * wheelDiameter / 1000));

		// Idle
		if (rpm < rpmIdle) {
			rpm = oldRpm;
			speed = oldSpeed;
		}
		
		// Gear shifter
		if (rpm > rpmRedzone) {
			gearMeter.classList.add('redzone');

		} else {
			gearMeter.classList.remove('redzone');
		}
		
		// Update GUI
		
		speedMeter.setValue(speed);
		rpmMeter.setValue(rpm);

		// Update engine sound
		if (source) {
			source.playbackRate.value = rpm / 4000;
		}

		if (source2) {
			source2.playbackRate.value = speed / 500;
		}

	})();
	
	///////////////////////////////////////////////
	// WEBAUDIO
	
	// Courtesy of https://mdn.github.io/decode-audio-data/
	
	// define variables

	var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
	var source,source2,
			gainNode;
	var songLength;

	var loader = document.querySelector('.loader');
	var btnVolume = document.querySelector('.btn-volume');

	// use XHR to load an audio track, and
	// decodeAudioData to decode it and stick it in a buffer.
	// Then we put the buffer into the source

	function getData() {
		source = audioCtx.createBufferSource();
		source2 = audioCtx.createBufferSource();
		let request = new XMLHttpRequest();

		request.open('GET', motorSamplePath, true);
		request.responseType = 'arraybuffer';

		request.onload = function() {
			var audioData = request.response;

			audioCtx.decodeAudioData(audioData, function(buffer) {
				let myBuffer = buffer;	// local buffer ?
				let myBuffer2 = buffer;
//				songLength = buffer.duration; // in seconds
				source.buffer = myBuffer;
				source2.buffer = myBuffer2;

				source.loop = true;
				source2.loop = true;

				// Hacky granular engine sound!
				source.loopStart = 0.1; // Tune this
				source.loopEnd = 0.1735; // Tune this

				source2.loopStart = 0.605;
				source2.loopEnd = 0.650;
				
				source.playbackRate.value = 1;
				source2.playbackRate.value = 1;

				// Create a gain node.
				gainNode = audioCtx.createGain();
				// Connect the source to the gain node.
				source.connect(gainNode);
				source2.connect(gainNode);
				// Connect the gain node to the destination.
				gainNode.connect(audioCtx.destination);

				// Remove loader
				loader.classList.remove('active');
			},

				function(e){"Error with decoding audio data" + e.err});
		}

		request.send();
	}

	// wire up buttons

	btnVolume.onclick = function() {
		this.classList.toggle('active');

		if (this.classList.contains('active')) {
			gainNode.gain.value = 1;
		} else {
			gainNode.gain.value = 0;
		}
	}

	// Load the sample
	getData();
	// Launch loop playing
	source.start(0);
	source2.start(0);
	
	
});
              
            
!
999px

Console