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                <p>Move your mouse left and right at different speeds.</p>
<div id="slider_input" class="slider">
  <div class="slider_indicator"></div>
<div id="slider_output" class="slider">
  <div class="slider_indicator"></div>
<p id="output"></p>


                html {
  background-color: #CC6633;
  font-family: "Fira Mono",Monaco,"Andale Mono","Lucida Console","Bitstream Vera Sans Mono","Courier";
  user-select: none;
  -moz-user-select: none;
  -khtml-user-select: none;
  -webkit-user-select: none;
  -o-user-select: none;

.slider {
  margin: 10px;
  width: 400px;
  height: 16px;
  background: rgba(0,0,0,.3);
  position: relative;

.slider_indicator {
  width: 16px;
  height: 16px;
  background: #000;
  position: absolute;


// scroll to bottom to see responsiveAnalogRead() function

// consts for demo
var SLIDER_WIDTH = 400;
var NOISE = 0.003;

// vars for demo
var mouseX = 0;
var globalSnap = 0;
var responsiveValue = 0;

// set up HTML elements and JS events for demo

var output = $('#output');
var sliderIndicatorInput = $('#slider_input > div');
var sliderIndicatorOutput = $('#slider_output > div');

var updateSlider = function(slider, value) {
  var sliderLeft = value / (ANALOG_RESOLUTION - 1) * SLIDER_WIDTH - 8;
  slider.css('left', sliderLeft+'px');

var begin = function() {
  var loop = function() {
    var newValue = analogRead();
    responsiveValue = responsiveAnalogRead(newValue);

    // update sliders
    updateSlider(sliderIndicatorInput, newValue);
    updateSlider(sliderIndicatorOutput, responsiveValue);

    // output status
    var outputText = "analogRead: " + newValue + "<br>";
    outputText += "responsiveAnalogRead: " + responsiveValue + "<br><br>";
    outputText += "snap: "+parseFloat(globalSnap).toFixed(2)+"<br>";

  // event handlers
  $(window).mousemove(function( event ) {
    mouseX = event.pageX;

  // begin loop

// Define fake Arduino millis() and analogRead() functions

var millis = function() {
  var d = new Date();
  return d.getTime(); 

var analogRead = function() {
  // get input from 0 - 1
  var input = Math.max(0,Math.min(mouseX - 10,SLIDER_WIDTH)) / SLIDER_WIDTH;
  // add noise to input
  input += (Math.random() - 0.5) * 2 * NOISE;
  input = Math.max(0, Math.min(1, input));
  // simulate analog read
  return Math.floor(input * (ANALOG_RESOLUTION - 1));

// consts

// affects the curve of movement amount > snap amount
// smaller amounts like 0.001 make it ease slower
// larger amounts like 0.1 make it less smooth
var SNAP_MULTIPLIER = 0.007;

// vars for responsiveAnalogRead

var smoothValue = 0;

// responsive analog read

var responsiveAnalogRead = function(newValue) {
  // get difference between new input value and current smooth value
  var diff = Math.abs(newValue - smoothValue);
  // now calculate a 'snap curve' function, where we pass in the diff (x) and get back a number from 0-1. We want small values of x to result in an output close to zero, so when the smooth value is close to the input value it'll smooth out noise aggressively by responding slowly to sudden changes. We want a small increase in x to result in a much higher output value, so medium and large movements are snappy and responsive, and aren't made sluggish by unnecessarily filtering out noise. A hyperbola (f(x) = 1/x) curve is used. First x has an offset of 1 applied, so x = 0 now results in a value of 1 from the hyperbola function. High values of x tend toward 0, but we want an output that begins at 0 and tends toward 1, so 1-y flips this up the right way. Finally the result is multiplied by 2 and capped at a maximum of one, which means that at a certain point all larger movements are maximally snappy
  var snapCurve = function(x) {
    var y = 1 / (x + 1);
    y = (1 - y)*2;
    if(y > 1) {
      return 1;
    return y;
  // multiply the input by SNAP_MULTIPLER so input values fit the snap curve better.
  var snap = snapCurve(diff * SNAP_MULTIPLIER);
  // (update globalSnap so we can show snap in the output window)
  globalSnap = snap;
  // calculate the exponential moving average based on the snap
  smoothValue += (newValue - smoothValue) * snap;
  // expected output is an integer
  return Math.floor(smoothValue);

// begin demo