<div class="toggle-container green">
  <input class="toggle-checkbox" type="checkbox">
  <div class="toggle-track">  
    <div class="toggle-thumb"></div>
  </div>
</div>

<div class="toggle-container blue">
  <input class="toggle-checkbox" type="checkbox">
  <div class="toggle-track">  
    <div class="toggle-thumb"></div>
  </div>
</div>

<div class="toggle-container boo">
  <input class="toggle-checkbox" type="checkbox">
  <div class="toggle-track">  
    <div class="toggle-thumb"></div>
  </div>
</div>

body {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 1em;
  min-height: 100vh;
  font-size: 2em;
}

@function em($pixels) {
  @if not (unit($pixels) == 'px') {
    @error 'Property #{$pixels} must have `px` unit.';
  }
  
  @return $pixels / 16px * 1em;
}

.toggle-container {
  position: relative;
  border-radius: em(50px);
  width: em(52px);
  height: em(30px);
}

.toggle-checkbox {
  -webkit-appearance: none;
  appearance: none;
  position: absolute;
  z-index: 1;
  border-radius: inherit;
  width: 100%;
  height: 100%;
  opacity: 0;
  cursor: pointer;
}

.toggle-track {
  display: flex;
  align-items: center;
  position: relative;
  border-radius: inherit;
  padding: em(4px);
  width: 100%;
  height: 100%;
  background-color: #aeaeae;
  box-shadow: inset 0 em(1px) em(2px) rgb(0 0 0 / .2);
  transition: background-color .4s linear;
  
  .toggle-container.green > .toggle-checkbox:checked + & {
    background-color: #4ccf59;
  }
    
  .toggle-container.blue > .toggle-checkbox:checked + & {
    background-color: #3384fb;
  }
    
  .toggle-container.boo > .toggle-checkbox:checked + & {
    background-color: #ff3372;
  }
}

.toggle-thumb {
  position: relative;
  border-radius: em(11px);
  transform-origin: left;
  width: em(22px);
  height: em(22px);
  background-color: #fff;
  box-shadow:
    0 em(4px) em(4px) rgb(0 0 0 / .2),
    inset 0 em(-2px) em(4px) rgb(0 0 0 / .2),
  ;
  
  .toggle-checkbox.toggled-once + .toggle-track > & {
    animation-name: grow-out, bounce-out;
    animation-duration: .2s;
    animation-timing-function: cubic-bezier(.75, 0, 1, 1), cubic-bezier(0, 0, 0.3, 1.5);
    animation-delay: 0s, .2s;
    animation-fill-mode: forwards;
  }
  
  .toggle-checkbox.toggled-once:checked + .toggle-track > & {
    animation-name: grow-in, bounce-in;
  }
  
  .toggle-container.boo & {
    &::after {
      content: '';
      position: absolute;
      top: 0;
      left: 0;
      border-radius: inherit;
      width: 100%;
      height: 100%;
      background-image: url('https://assets.codepen.io/4175254/boo-face.png');
      background-size: (14 * 100 / 22 * 1%) (12 * 100 / 22 * 1%);
      background-position: center;
      background-repeat: no-repeat;
      box-shadow: inset 0 em(-2px) em(4px) rgb(0 0 0 / .2);
      image-rendering: pixelated;
      opacity: 0;
      transition: opacity .2s linear;
      
      @at-root {
        .toggle-container.boo > .toggle-checkbox:checked + .toggle-track > .toggle-thumb::after {
          opacity: 1;
        }
        
        @media (hover: hover) {
          .toggle-container.boo > .toggle-checkbox:hover + .toggle-track > .toggle-thumb::after {
            opacity: 1;
          }
        }
      }
    }
  }
}

@keyframes grow-in {
  0% {
    border-radius: em(11px);
    transform: translateX(0) scale(1);
  }
  100% {
    border-radius: em(1 / (34 / 22) * 11px) #{'/'} em(1 / (16 / 22) * 11px);
    transform: translateX(em(8px)) scale((34 / 22), (16 / 22));
  }
}

@keyframes bounce-in {
  0% {
    border-radius: em(1 / (34 / 22) * 11px) #{'/'} em(1 / (16 / 22) * 11px);
    transform: translateX(em(8px)) scale((34 / 22), (16 / 22));
  }
  100% {
    border-radius: em(11px);
    transform: translateX(100%) scale(1);
  }
}

@keyframes grow-out {
  0% {
    border-radius: em(11px);
    transform: translateX(100%) scale(1);
  }
  100% {
    border-radius: em(1 / (34 / 22) * 11px) #{'/'} em(1 / (16 / 22) * 11px);
    transform: translateX(em(2px)) scale((34 / 22), (16 / 22));
  }
}

@keyframes bounce-out {
  0% {
    border-radius: em(1 / (34 / 22) * 11px) #{'/'} em(1 / (16 / 22) * 11px);
    transform: translateX(em(2px)) scale((34 / 22), (16 / 22));
  }
  100% {
    border-radius: em(11px);
    transform: translateX(0) scale(1);
  }
}

const checkboxes = document.querySelectorAll('input[type="checkbox"]');

const detectToggleOnce = (e) => {
  e.target.classList.add('toggled-once');
};

checkboxes.forEach(checkbox => {
  checkbox.addEventListener('click', detectToggleOnce, { once: true });
});