<input type="checkbox" id="switch" />
<div id="app">
  <header class="ui-header">
    <i class="fa fa-chevron-left"></i>
    <div class="ui-text -app-title">App Settings</div>
    <div class="ui-text">Apply</div>
  </header>
  <main class="ui-content">
    <div class="ui-discounts">
      <i class="fa fa-codepen"></i>
      <div class="ui-text">Get hottest discounts</div>
    </div>
    <div class="ui-value">
      <div class="ui-digit" id="num1"></div>
      <div class="ui-digit" id="num2"></div>
    </div>
    <div class="ui-panel">
      <div class="ui-range-ticks">
        <div class="ui-range-tick" data-value="0"></div>
        <div class="ui-range-tick" data-value="3"></div>
        <div class="ui-range-tick" data-value="6"></div>
        <div class="ui-range-tick" data-value="9"></div>
        <div class="ui-range-tick" data-value="12"></div>
      </div>
      <div class="ui-range" id="rangeTrack">
        <input
          type="range"
          id="range"
          class="ui-range-input"
          min="0"
          max="12"
          step="1"
          value="6"
        />
        <div class="ui-range-track">
          <div class="ui-range-thumb"></div>
        </div>
      </div>
      
      <div class="ui-controls">
        <div class="ui-switch">
          <label
            class="ui-switch-track"
            for="switch"
            title="Turn smooth range thumb on/off"
          >
          </label>
        </div>
      </div>
      
      <div class="ui-footer">
        <i class="fa fa-shopping-bag"></i>
        <i class="fa fa-cart-arrow-down"></i>
        <i class="fa fa-filter"></i>
        <i class="fa fa-gear"></i>
      </div>
    </div>
  </main>
</div>
@import url('https://fonts.googleapis.com/css?family=Open+Sans:300,700');

$max-value: 12;
$num-shift: 10vh;
$num-size: 24vh;
$start-value: 6;

$color-gray: #B5B5B5;

:root {
  --value-progress: calc(var(--value, #{$start-value}) / #{$max-value});
  font-family: Open Sans, sans-serif;
  font-weight: 300;
  font-size: 2.5vh;
}

#app {
  height: 96vh;
  width: 54vh;
  background: linear-gradient(
    to top right,
    hsl(360, 90%, 68%),
    hsl(31, 100%, 51%),
    #EC4E91,
    #9535D3,
    #4DACFF
  );
  background-size: 400% 400%;
  background-position: calc(var(--value-progress) * 100%) 0;
  color: white;
  user-select: none;
  overflow: hidden;
  box-shadow: 0 0 4vh rgba(black, 0.1);
  
  @media
    (max-width: 740px)
    and (-webkit-min-device-pixel-ratio: 2)
    and (orientation: portrait) {
    width: 100%;
    height: 100%;
  }
}

$header-height: 8vh;
.ui-header {
  height: $header-height;
  width: 100%;
  display: flex;
  flex-direction: row;
  justify-content: space-between;
  align-items: center;
  padding: 2vh;
  background: white;
  color: $color-gray;
  
  > * {
    width: 25%;
    flex: 0 0 25%;
  }
  
  > .ui-text.-app-title {
    text-align: center;
    flex: 1 0 auto;
    white-space: nowrap;
  }
  
  > .ui-text:last-child {
    text-align: right;
  }
}

.ui-content {
  flex: 1 0 100%;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  align-items: center;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  padding-top: $header-height;
}

.ui-discounts {
  padding: 2vh 0;
  text-align: center;
  width: calc(100% - 6vh);
  margin: 0 2vh;
  border-bottom: 1px solid rgba(white, 0.25);
  
  > .ui-text {
    margin: 1vh 0;
    line-height: 1;
    letter-spacing: 0.5px;
  }
}

.ui-value {
  height: $num-size;
  width: $num-size * 1.2;
  line-height: $num-size;
  margin: 2vh 0;
  font-weight: 700;
  
  &:before, &:after {
    display: block;
    position: absolute;
    height: 4vh;
    line-height: 4vh;
    top: calc(50% - 2vh);
    font-weight: 300;
    font-size: 2.5vh;
    letter-spacing: 0.5px;
    transition: transform 0.6s ease;
  }
  &:before {
    content: 'Every';
    right: 100%;
    transform: translateX(calc(var(--changing) * -50%));
  }
  &:after {
    content: 'hours';
    left: 100%;
    transform: translateX(calc(var(--changing) * 50%));
  }
}

.ui-digit {
  position: absolute;
  font-size: $num-size;
  width: 100%;
  text-align: center;
  height: 100%;
  user-select: none;
}

#num1 {
  transform:
    translateX(calc(var(--progress, 0) * -#{$num-shift}))
    scale(calc(1 + var(--progress, 0)));
  opacity: calc(1 - var(--progress, 0));
  filter: blur(calc(var(--progress) * 2px));
}

#num2 {
  transform:
    translateX(calc(var(--progress, 0) * -#{$num-shift} + #{$num-shift}))
    scale(calc(var(--progress, 0)));
  opacity: var(--progress, 0);
}

.ui-panel {
  width: 100%;
}

.ui-controls {
  background: white;
  padding: 6vh 4vh;
}

.ui-switch {
  margin: 0 auto;
  top: 2vh;
  width: 8vh;
  height: 4vh;
  border-radius: 4vh;
  background-image: linear-gradient(
    to right,
    #FF6850,
    #FF8A2B
  );
  
  &:before, &:after {
    position: absolute;
    color: #656565;
    margin: 0 2vh;
    height: 2vh;
    top: calc(50% - 1vh);
    display: block;
    font-size: 2vh;
    line-height: 2vh;
    letter-spacing: 0.5px;
  }
  &:before {
    content: 'Off';
    right: 100%;
  }
  &:after {
    content: 'On';
    left: 100%;
  }
}

input#switch {
  position: absolute;
  opacity: 0;
  pointer-events: none;

  &:checked + #app {
    * {
      .ui-switch-track {
        transform: translateX(-2vh) scale(0.8);
      }

      .ui-range-track {
        display: none;
      }
    }
  }
  
  &:not(:checked) + #app {
    --thumb-opacity: 0;
  }
}

.ui-switch-track {
  position: absolute;
  top: 0;
  left: calc(50% - 2vh);
  width: 4vh;
  height: 4vh;
  border-radius: 50%;
  border: 0.5vh solid rgba(white, 0.1);
  background: white;
  display: block;
  transform: translateX(2vh) scale(0.8);
  transition: transform 0.3s ease;
  box-shadow: 0 0 1vh rgba(black, 0.1);
}

.ui-range {
  width: 100%;
  background: white;
  z-index: 1;
  
  > input {
    position: absolute;
    z-index: 1;
    top: -3vh;
  }
}

.ui-range-track {
  position: absolute;
  top: 1vh;
  width: calc(100% - 8vh);
  transform:
    translateX(calc(var(--value, #{$start-value}) / 12 * 100% - 50%));
  left: 4vh;
  z-index: 1;
  pointer-events: none;
  
  &:before, &:after {
    content: '';
    position: absolute;
    width: 8vh;
    height: 8vh;
    border-radius: 50%;
    top: -4vh;
    left: calc(50% - 4vh);
    background: white;
  }
  
  &:before {
    transform: scale(1.2);
  }
  
  &:after {
    content: "\f1cb";
    font-family: FontAwesome;
    font-size: 4vh;
    line-height: 8vh;
    color: #FF6850;
    text-align: center;
    top: -4vh;
    box-shadow: 0 0.5vh 2vh 0.5vh rgba(black, 0.1);
  }
}

.ui-range-ticks {
  width: 100%;
  height: 3vh;
  margin-bottom: 6vh;
  display: flex;
  flex-direction: row;
  justify-content: space-between;
  padding: 0 2vh;
}

.ui-range-tick {
  width: 4vh;
  transform:
    translateY(calc(var(--proximity) * 1vh - 1vh));
  
  &:before {
    content: attr(data-value);
    display: block;
    width: 100%;
    text-align: center;
    transform: scale(calc((2 - var(--proximity)) / 3 + 1));
    transform-origin: bottom center;
  }
  &:after {
    content: '';
    position: absolute;
    display: block;
    width: 1px;
    height: 1vh;
    background: white;
    left: calc(50% - 0.5px);
    top: calc(100% + 1vh);
    transform: translateY(calc(var(--proximity) * 0.5vh - 0.5vh));
  }
}

.ui-footer {
  color: $color-gray;
  background: white;
  padding: 1rem 0;
  display: flex;
  flex-direction: row;
  justify-content: space-around;
  align-items: center;
  box-shadow: 0 -0.5rem 1rem rgba(gray, 0.1);
  z-index: 1;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  background-image: linear-gradient(to bottom right, white, #E7E7EF);
}

html, body {
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
}

svg {
  display: none;
}

*, *:before, *:after {
  box-sizing: border-box;
  position: relative;
}



// source: https://css-tricks.com/styling-cross-browser-compatible-range-inputs-css/
// thanks, @danieljackstern !!
$track-color: #EFEFEF !default;
$thumb-color: white !default;

$thumb-radius: 8vh !default;
$thumb-height: 8vh !default;
$thumb-width: 8vh !default;
$thumb-shadow-size: 4px !default;
$thumb-shadow-blur: 0.5vh !default;
$thumb-shadow-color: rgba(black, 0.1) !default;
$thumb-border-width: 0 !default;
$thumb-border-color: #eceff1 !default;

$track-width: 100% !default;
$track-height: 1px !default;
$track-shadow-size: 0 !default;
$track-shadow-blur: 0 !default;
$track-shadow-color: rgba(0, 0, 0, .2) !default;

$track-radius: 0 !default;
$contrast: 5% !default;

@mixin shadow($shadow-size, $shadow-blur, $shadow-color) {
  box-shadow: $shadow-size $shadow-size $shadow-blur $shadow-color, 0 0 $shadow-size lighten($shadow-color, 5%);
}

@mixin track {
  cursor: pointer;
  height: $track-height;
  transition: all .2s ease;
  width: $track-width;
  opacity: --thumb-opacity;
}

@mixin thumb {
  box-shadow: 0 0.5vh 2vh 0.5vh rgba(black, 0.1);
  background: $thumb-color;
  border: $thumb-border-width solid $thumb-border-color;
  border-radius: $thumb-radius;
  cursor: pointer;
  height: $thumb-height;
  width: $thumb-width;
  opacity: var(--thumb-opacity, 1);
}

[type='range'] {
  -webkit-appearance: none;
  margin: $thumb-height / 2 0;
  width: $track-width;

  &:focus {
    outline: 0;

    &::-webkit-slider-runnable-track {
      background: lighten($track-color, $contrast);
    }

    &::-ms-fill-lower {
      background: $track-color;
    }

    &::-ms-fill-upper {
      background: lighten($track-color, $contrast);
    }
  }

  &::-webkit-slider-runnable-track {
    @include track;
    @include shadow($track-shadow-size, $track-shadow-blur, $track-shadow-color);
    background: $track-color;
  }

  &::-webkit-slider-thumb {
    @include thumb;
    -webkit-appearance: none;
    margin-top: calc(#{$track-height / 2} - #{$thumb-height / 2});
  }

  &::-moz-range-track {
    @include track;
    @include shadow($track-shadow-size, $track-shadow-blur, $track-shadow-color);
    background: $track-color;
  }

  &::-moz-range-thumb {
    @include thumb;
  }

  &::-ms-track {
    @include track;
    background: transparent;
    border-color: transparent;
    border-width: ($thumb-height / 2) 0;
    color: transparent;
  }

  &::-ms-fill-lower {
    @include shadow($track-shadow-size, $track-shadow-blur, $track-shadow-color);
    background: darken($track-color, $contrast);
  }

  &::-ms-fill-upper {
    @include shadow($track-shadow-size, $track-shadow-blur, $track-shadow-color);
    background: $track-color;
  }

  &::-ms-thumb {
    @include thumb;
    margin-top: 0;
  }
}
const range = document.querySelector('#range');
const rangeTrack = document.querySelector('#rangeTrack');
const value = document.querySelector('.ui-value');
const num1 = document.querySelector('#num1');
const num2 = document.querySelector('#num2');
const ticks = document.querySelectorAll('.ui-range-tick');
const docStyle = document.documentElement.style;

const { fromEvent, interval } = Rx.Observable;

const clamp = (min, max) => val => Math.min(Math.max(val, min), max);

const lerp = (curr, next) => {
  const delta = (next - curr);
  if (Math.abs(delta) < 0.01) return curr;
  return curr + (next - curr) * 0.13;
};

const touch$ = fromEvent(range, 'input');

const touchEnd$ = fromEvent(range, 'mouseup')
  .merge(fromEvent(range, 'touchend'))
  .mapTo(false);

const change$ = touch$
  .mapTo(true)
  .merge(touchEnd$)
  .distinctUntilChanged();
  
const num$ = touch$
  .map(e => +e.target.value)
  .distinctUntilChanged()
  .startWith(6);

const af$ = interval(0, Rx.Scheduler.animationFrame);

const smoothNum$ = af$
  .withLatestFrom(num$, (_, num) => num)
  .scan(lerp)
  .distinctUntilChanged();

const progress$ = smoothNum$
  .map(num => num - Math.floor(num));

smoothNum$.subscribe(num => {
  num1.innerHTML = Math.floor(num);
  num2.innerHTML = Math.ceil(num);
  docStyle.setProperty('--value', num);

  Array.from(ticks).forEach((tick) => {
    const proximity = Math.min(
      Math.abs(tick.getAttribute('data-value') - num), 2);
    tick.style.setProperty('--proximity', proximity);
  });
});

progress$.subscribe(progress => {
  docStyle.setProperty('--progress', progress);
  
  if (navigator.userAgent.toLowerCase().indexOf('firefox') > -1) {
    // Firefox does not support custom properties
    // inside of scale() for whatever reason
    num1.setAttribute('style', `
      transform:
        translateX(calc(${progress} * -10vh))
        scale(${1 + progress});
      opacity: ${1 - progress};

    `);
    
    num2.setAttribute('style', `
      transform:
        translateX(calc(${progress} * -10vh + 10vh))
        scale(${progress});
      opacity: ${progress};
    `);
  }
});

change$.subscribe(changing => {
  num1.parentElement.style.setProperty('--changing', +changing);
});
View Compiled

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://unpkg.com/@reactivex/rxjs@5.1.1/dist/global/Rx.min.js