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HTML 

              
                <!-- Keep dragging over the maximum value unlock a secret level  -->
<div class="slider-wrapper">
  <div class="slider-track">
    <input class="slider-input" type="range" value="100">  
    <div class="slider-thumb">
      <svg class="slider-thumb-image" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 176 176">
        <path d="M109.621 58.624c-2.248-1.8-5.008-2.962-7.793-3.69-55.136-14.399-18.22 90.985-88.17 59.012-.306-.14-.621-.334-.907-.511-3.895-2.411-8.839 1.419-6.676 5.669 37.499 73.676 140.46-6.692 111.993-50.336-1.504-2.305-3.109-4.594-4.889-6.692a25.95 25.95 0 0 0-3.558-3.453z" filter="url(#A)"/>
        <path d="M108.983 52.653c-15.728-4.464-34.22 2.06-36.123 4.369 14.141-.161 22.213-.751 29.185 10.25 12.719-.852 17.221 3.27 24.322 18.322 1.953-14.872-6.86-27.522-12.263-30.83 14.395-43.021.099-41.872-10.808-39.269 9.985 19.97 9.585 27.874 5.687 37.158z" fill="#35890e" filter="url(#B)"/>
        <path d="M80.361 65.109c4-4.4 8.333-.833 10 1.5-8.799-3.2-18.667 17.667-22.501 28.5 2.5-8.167 8.501-25.6 12.501-30z" fill="#fff" fill-opacity=".4"/>
        <defs>
          <filter id="A" x="3.547" y="49.575" width="124.432" height="107.417" filterUnits="userSpaceOnUse" color-interpolation-filters="sRGB">
            <feFlood flood-opacity="0"/>
            <feBlend in="SourceGraphic" result="B"/>
            <feColorMatrix in="SourceAlpha" values="0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 127 0" result="C"/>
            <feOffset dx="-2" dy="-4"/>
            <feGaussianBlur stdDeviation="10"/>
            <feComposite in2="C" operator="arithmetic" k2="-1" k3="1"/>
            <feColorMatrix values="0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.6 0"/>
            <feBlend in2="B" result="D"/>
            <feColorMatrix in="SourceAlpha" values="0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 127 0" result="C"/>
            <feOffset dx="5" dy="8"/>
            <feGaussianBlur stdDeviation="10"/>
            <feComposite in2="C" operator="arithmetic" k2="-1" k3="1"/>
            <feColorMatrix values="0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0.25 0"/>
            <feBlend in2="D"/>
          </filter>
          <filter id="B" x="72.86" y="10.442" width="53.784" height="77.152" filterUnits="userSpaceOnUse" color-interpolation-filters="sRGB">
            <feFlood flood-opacity="0"/>
            <feBlend in="SourceGraphic" result="B"/>
            <feColorMatrix in="SourceAlpha" values="0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 127 0" result="C"/>
            <feOffset dy="-4"/>
            <feGaussianBlur stdDeviation="6"/>
            <feComposite in2="C" operator="arithmetic" k2="-1" k3="1"/>
            <feColorMatrix values="0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.45 0"/>
            <feBlend in2="B" result="D"/>
            <feColorMatrix in="SourceAlpha" values="0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 127 0" result="C"/>
            <feOffset dy="2"/>
            <feGaussianBlur stdDeviation="3"/>
            <feComposite in2="C" operator="arithmetic" k2="-1" k3="1"/>
            <feColorMatrix values="0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0.25 0"/>
            <feBlend in2="D"/>
          </filter>
        </defs>
      </svg>
    </div>
  </div>
</div>
!

CSS 

              
                body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background-color: #fff;
  font-size: 3em;
}

.slider-wrapper {
  --slider-height: .3125em;
  --slider-thumb-size: 1.75em;
  --slider-progress: 50;
  border-radius: 50px;
  width: 7em;
  max-width: 100%;
  transition: width .2s;
  
  &.unlocked {
    width: 8em;
  }
}

.slider-track {
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
  border-radius: inherit;
  width: 100%;
  height: var(--slider-height);
  background-image:
    linear-gradient(
      to right,
      transparent 0% calc(var(--slider-progress) * 1%),
      #aaa calc(var(--slider-progress) * 1%) 100%,
    ),
    linear-gradient(to right, #62ad1d, #fbbd1e, #fb6e1e, #e71a1a, #220000),
  ;
  background-size: auto, 125% 100%;
  box-shadow:
    inset 0 2px 4px rgb(255 255 255 / .6),
    inset 0 -2px 4px rgb(0 0 0 / .1),
    0 2px 4px rgb(0 0 0 / .1),
  ;
  transition: background-size .2s;
  
  .slider-wrapper.unlocked > & {
    background-size: auto, 100% 100%;
  }
}

.slider-input {
  -moz-appearance: none;
  -webkit-appearance: none;
  appearance: none;
  position: absolute;
  z-index: 1;
  left: 50%;
  transform: translate(-50%);
  border-radius: inherit;
  width: calc(100% + var(--slider-thumb-size));
  height: 100%;
  opacity: 0;
  cursor: pointer;

  &::-webkit-slider-runnable-track {
    height: 100%;
  }
  
  @mixin thumb {
    -moz-appearance: none;
    -webkit-appearance: none;
    appearance: none;
    margin-top: calc((var(--slider-height) / 2) - (var(--slider-thumb-size) / 2));
    border-width: 0;
    border-radius: 50%;
    width: var(--slider-thumb-size);
    height: var(--slider-thumb-size);
  }
  
  &::-webkit-slider-thumb {
    @include thumb;
  }
  
  &::-moz-range-thumb {
    @include thumb;
  }
}

.slider-thumb {
  display: flex;
  justify-content: center;
  align-items: center;
  position: absolute;
  left: calc(var(--slider-progress) / 100 * (100% - var(--slider-height)) + var(--slider-height) / 2);
  left: calc(var(--slider-progress) * 1%);
  transform: translateX(-50%);
  width: var(--slider-thumb-size);
  height: var(--slider-thumb-size);
  transition: transform .2s;
  
  .slider-input:active + & {
    transform: translateX(-50%) scale(.86);
  }
  
  &::after {
    content: '';
    position: absolute;
    z-index: 1;
    width: 150%;
    height: 150%;
    background-image: url('https://assets.codepen.io/4175254/explosion-2.png');
    background-size: 800%;
    opacity: 0;
  }
  
  &.play-explosion::after {
    animation: explosion .5s steps(8) forwards;
    opacity: 1;
  }
}

@keyframes explosion {
  to {
    background-position-x: -800%;
  }
}

.slider-thumb-image {
  --slider-thumb-image-color: rgb(251 150 30);
  position: relative;
  width: 100%;
  height: 100%;
  fill: var(--slider-thumb-image-color);
  transition: transform .2s;
  
  &.shake {
    animation: shake .2s infinite;
  }
}

@keyframes shake {
  0% {
    transform: rotate(0deg);
  }
  25% {
    transform: rotate(5deg);
  }
  50% {
    transform: rotate(0eg);
  }
  75% {
    transform: rotate(-5deg);
  }
  100% {
    transform: rotate(0deg);
  }
}
!

JS 

              
                const sliderWrapper = document.querySelector('.slider-wrapper');
const sliderInput = document.querySelector('.slider-input');
const sliderTrack = document.querySelector('.slider-track');
const sliderThumb = document.querySelector('.slider-thumb');
const sliderThumbImage = document.querySelector('.slider-thumb-image');
  
const minValue = +sliderInput.min || 0;
const maxValue = +sliderInput.max || 100;

const colorStops = [
  { r: 98, g: 173, b: 29 },
  { r: 251, g: 189, b: 30 },
  { r: 251, g: 110, b: 30 },
  { r: 231, g: 26, b: 26 },
];

const setSliderThumbImageColor = (progress) => {
  const index = (colorStops.length - 1) * progress / 100;
  const startIndex = Math.floor(index);
  const endIndex = Math.ceil(index);

  const startColor = colorStops[startIndex];
  const endColor = colorStops[endIndex];

  const percentage = index - startIndex;

  const [r, g, b] = [
    Math.round(startColor.r + (endColor.r - startColor.r) * percentage),
    Math.round(startColor.g + (endColor.g - startColor.g) * percentage),
    Math.round(startColor.b + (endColor.b - startColor.b) * percentage)
  ];

  sliderThumbImage.style.setProperty('--slider-thumb-image-color', `rgb(${r} ${g} ${b})`);
};

const updateSlider = () => {
  const progress = 100 * +sliderInput.value / (maxValue - minValue);
  sliderWrapper.style.setProperty('--slider-progress', progress);
  setSliderThumbImageColor(progress);
}

sliderInput.addEventListener('input', updateSlider);

updateSlider();

let pointerHoldingRightTimer;
let isTimerRunning = false;

const detectPointerHoldingRight = (event) => {
  const isSliderAtMax = +sliderInput.value === maxValue;
  
  const sliderRect = sliderWrapper.getBoundingClientRect();
  const pointerX = event.clientX;
  const offset = 40;
  const isPointerOnSliderRight = pointerX >= (sliderRect.right + offset);
  
  if (isSliderAtMax && isPointerOnSliderRight) {
    if (!isTimerRunning) {
      isTimerRunning = true;
      sliderThumbImage.classList.add('shake');
      pointerHoldingRightTimer = setTimeout(() => {
        sliderInput.removeEventListener('pointerdown', detectSecret);
        colorStops.push({ r: 34, g: 0, b: 0 });
        sliderWrapper.classList.add('unlocked');
        sliderThumb.addEventListener('animationend', () => {
          sliderThumb.classList.remove('play-explosion');
        });
        sliderThumb.classList.add('play-explosion');
        setSliderThumbImageColor(100);
        sliderThumbImage.classList.remove('shake');
      }, 1000); 
    }
  } else {
    clearTimeout(pointerHoldingRightTimer);
    isTimerRunning = false;
    sliderThumbImage.classList.remove('shake');
  }
};

const detectSecret = () => {
  window.addEventListener('pointermove', detectPointerHoldingRight);
  sliderInput.addEventListener('pointerup', () => {
    window.removeEventListener('pointermove', detectPointerHoldingRight);
    clearTimeout(pointerHoldingRightTimer);
    sliderThumbImage.classList.remove('shake');
  });
}

sliderInput.addEventListener('pointerdown', detectSecret);
!
999px

Console