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  <label for="h">Hue<span>(0 - 360)</span></label>
  <input type="number" id="h" value="0" />
  <label for="h">Saturation<span>(0 - 100%)</span></label>
  <input type="number" id="s" value="50" />
  <label for="h">Lightness<span>(0 - 100%)</span></label>
  <input type="number" id="l" value="50" />

<footer>hsl(<span id="hdisplay"></span>, <span id="sdisplay"></span>, <span id="ldisplay"></span>)


                :root {
  --h: 0;
  --s: 50;
  --l: 50;

body {
  background: hsl(var(--h), calc(var(--s) * 1%), calc(var(--l) * 1%));

#hdisplay::after {
  counter-reset: hcount var(--h);
  content: counter(hcount);
#sdisplay::after {
  counter-reset: scount var(--s);
  content: counter(scount) '%';
#ldisplay::after {
  counter-reset: lcount var(--l);
  content: counter(lcount) '%';

/* Structure */
body {
  min-height: 100vh;
  overflow: hidden;
  display: flex;
  justify-content: center;
  align-items: flex-end;
  font-family: -apple-system, system-ui;
  font-size: 82.5%;

div {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-end;
  background: hsla(0, 0%, 0%, .6);
  color: hsl(0, 100%, 100%);
  padding: 1rem .5rem 3rem;
input {
  height: 3rem;
  font-size: 2rem;
  width: 99%;
  text-align: center;
  position: relative;
  display: block;
  appearance: none;
  border-radius: 0;
  border: 0;
  background: transparent;
  color: hsl(0, 100%, 100%);
  border-bottom: .1rem solid currentColor; 
label {
  display: block;
  text-align: center;
label span {
  display: block;
  padding: .25rem 0;

footer {
  position: absolute;
  color: hsl(0, 0%, 100%);
  bottom: 0;
  left: 0;
  right: 0;
  text-align: center;
  padding: 1rem;


                //match the initial values of the CSS Variables
var hsl = {
  h: 0,
  s: 50,
  l: 50

var hinput = document.getElementById('h');
var sinput = document.getElementById('s');
var linput = document.getElementById('l');

Array.from(document.querySelectorAll('input')).forEach(function(item) {
  item.addEventListener('input', onNewValue);

function onNewValue(element) {
  if (element.tagName !== 'INPUT') {
    element = element.currentTarget;
  //input for h, s, or l?
  var which =;
  //current number value
  hsl[which] = element.value;
  //update CSS Variable value, which in turn updates the background color as well as the displayed hsl value at the bottom of the screen'--' + which, hsl[which]);

// When focused on Body
// Q/A to +/- Hue
// W/S to +/- Saturation
// E/D to +/- Lightness
document.body.addEventListener('keydown', function(e) {
  if (e.key === 'Q' || e.key === 'q') {
    updateValue(hinput, hsl.h);
  } else if (e.key === 'A' || e.key === 'a') {
    updateValue(hinput, hsl.h);
  } else if (e.key === 'W' || e.key === 'w') {
    updateValue(sinput, hsl.s);
  } else if (e.key === 'S' || e.key === 's') {
    updateValue(sinput, hsl.s);
  } else if (e.key === 'E' || e.key === 'e') {
    updateValue(linput, hsl.l);
  } else if (e.key === 'D' || e.key === 'd') {
    updateValue(linput, hsl.l);
function updateValue(el, val) {
  el.value = val;