<main>
  <div class="col">
    <label>
      <span class="switch">
        <input class="switch__input" type="checkbox" role="switch">
        <span class="switch__surface">
          <span class="switch__surface-glare"></span>
        </span>
        <span class="switch__inner-shadow"></span>
        <span class="switch__inner">
          <span class="switch__inner-glare"></span>
        </span>
        <span class="switch__rocker-shadow"></span>
        <span class="switch__rocker-sides">
          <span class="switch__rocker-sides-glare"></span>
        </span>
        <span class="switch__rocker">
          <span class="switch__rocker-glare"></span>
        </span>
        <span class="switch__light">
          <span class="switch__light-inner"></span>
        </span>
      </span>
      <span class="sr">Light Switch</span>
    </label>
  </div>
  <div class="col col--dark">
    <label>
      <span class="switch">
        <input class="switch__input" type="checkbox" role="switch">
        <span class="switch__surface">
          <span class="switch__surface-glare"></span>
        </span>
        <span class="switch__inner-shadow"></span>
        <span class="switch__inner">
          <span class="switch__inner-glare"></span>
        </span>
        <span class="switch__rocker-shadow"></span>
        <span class="switch__rocker-sides">
          <span class="switch__rocker-sides-glare"></span>
        </span>
        <span class="switch__rocker">
          <span class="switch__rocker-glare"></span>
        </span>
        <span class="switch__light">
          <span class="switch__light-inner"></span>
        </span>
      </span>
      <span class="sr">Dark Switch</span>
    </label>
  </div>
</main>

* {
  border: 0;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
:root {
  --hue: 223;
  --fg: hsl(var(--hue),10%,10%);
  --trans-dur: 0.3s;
  --trans-timing: cubic-bezier(0.83, 0, 0.17, 1);
  font-size: calc(30px + (60 - 30) * (100vw - 320px) / (2560 - 320));
}
body,
input {
  color: var(--fg);
  font: 1em/1.5 sans-serif;
}
body {
  display: flex;
  height: 100vh;
}
main,
label,
.col {
  display: flex;
}
main {
  flex-direction: column;
  width: 100%;
}
label {
  align-items: center;
  margin: auto;
  -webkit-tap-highlight-color: transparent;
}
.col {
  background-color: hsl(var(--hue),10%,90%);
  background-image: linear-gradient(hsla(0,0%,0%,0),hsla(0,0%,0%,0.4));
  padding: 1.5em;
  width: 100%;
  height: 100%;
}
.sr {
  overflow: hidden;
  position: absolute;
  width: 1px;
  height: 1px;
}

/* Light theme */
.switch,
.switch__input {
  display: block;
}
.switch {
  border-radius: 1.5em;
  box-shadow: 0 0.125em 0.25em hsla(0,0%,0%,0.4);
  position: relative;
  width: 4.5em;
  height: 3em;
  perspective: 10em;
}
.switch span {
  display: block;
}
.switch > span {
  border-radius: inherit;
  z-index: 1;
}
.switch__surface-glare,
.switch__inner,
.switch__inner-glare,
.switch__rocker-sides,
.switch__rocker-sides-glare,
.switch__rocker,
.switch__rocker-glare,
.switch__light {
  transition: transform var(--trans-dur) var(--trans-timing);
}
.switch__surface {
  background-color: hsl(var(--hue),10%,83%);
  overflow: hidden;
  width: 100%;
  height: 100%;
}
.switch > .switch__surface {
  z-index: 0;
}
.switch__surface-glare {
  background-image: radial-gradient(50% 50% at center,hsla(var(--hue),10%,90%,1),hsla(var(--hue),10%,90%,0));
  width: 3em;
  height: 3em;
  transform: translate(0,0.125em);
}
.switch__input {
  background-color: hsl(var(--hue),10%,80%);
  border-radius: 1.5em;
  box-shadow: 0 0 0 0.125em hsla(var(--hue),90%,50%,0);
  outline: transparent;
  position: absolute;
  top: 0.0625em;
  left: 0.0625em;
  width: calc(100% - 0.125em);
  height: calc(100% - 0.125em);
  transition: box-shadow 0.15s linear;
  z-index: 1;
  -webkit-appearance: none;
  appearance: none;
  -webkit-tap-highlight-color: transparent;
}
.switch__input:focus-visible {
  box-shadow: 0 0 0 0.125em hsla(var(--hue),90%,50%,1);
}
.switch__inner {
  background-color: hsl(var(--hue),10%,83%);
  overflow: hidden;
  position: absolute;
  inset: 0.5em;
  transform: translate(0.125em,0);
}
.switch__inner-glare {
  background-image: radial-gradient(50% 50% at center,hsla(var(--hue),10%,90%,1),hsla(var(--hue),10%,90%,0));
  position: absolute;
  width: 2em;
  height: 2em;
  transform: translate(100%,-0.5em);
}
.switch__inner-shadow {
  box-shadow: 0 0.125em 0.25em hsla(0,0%,0%,0.4);
  position: absolute;
  inset: 0.5em;
}
.switch__rocker-shadow {
  box-shadow: 0 0.125em 0.25em hsla(0,0%,0%,0.15);
  position: absolute;
  top: 0.5625em;
  right: 0.5625em;
  bottom: 0.5625em;
  left: 0.75em;
}
.switch__rocker-sides {
  background-color: hsl(var(--hue),10%,80%);
  overflow: hidden;
  position: absolute;
  inset: 0.5em;
  transform: rotateY(-20deg) translateZ(0.5em);
  transform-style: preserve-3d;
}
.switch__rocker-sides-glare {
  background-image: linear-gradient(90deg,hsla(var(--hue),10%,85%,0),hsla(var(--hue),10%,85%,1),hsla(var(--hue),10%,85%,0));
  position: absolute;
  width: 200%;
  height: 100%;
}
.switch__rocker {
  background-color: hsl(var(--hue),10%,80%);
  overflow: hidden;
  position: absolute;
  inset: 0.5625em;
  transform: rotateY(-20deg) translateZ(0.5em);
  transform-style: preserve-3d;
}
.switch__rocker-glare {
  background-image: linear-gradient(120deg,hsla(var(--hue),10%,85%,0) 25%,hsla(var(--hue),10%,85%,1) 50%,hsla(var(--hue),10%,85%,0) 75%);
  position: absolute;
  width: 100%;
  height: 100%;
  transform: translateX(-33%);
}
.switch__light {
  background-image: linear-gradient(-45deg,hsl(var(--hue),10%,60%) 30%,hsl(var(--hue),10%,80%));
  box-shadow: 0 0 max(1px,0.05em) hsla(var(--hue),10%,10%,0.3) inset;
  position: absolute;
  top: 50%;
  left: 50%;
  width: 0.5em;
  height: 0.5em;
  transform: translate(-50%,-50%) rotateY(-20deg) translateX(1.125em) translateZ(0.51em);
}
.switch__light-inner {
  background-color: hsl(133,90%,50%);
  box-shadow:
    0 0 max(1px,0.05em) hsla(var(--hue),10%,10%,0.3) inset,
    0 0 0.25em hsl(133,90%,50%);
  border-radius: 50%;
  opacity: 0;
  width: 100%;
  height: 100%;
  transition: opacity var(--trans-dur) var(--trans-timing);
}

/* Dark theme */
.col--dark {
  background-color: hsl(var(--hue),10%,10%);
  color: hsl(var(--hue),10%,90%);
}
.col--dark .switch__surface {
  background-color: hsl(var(--hue),10%,22%);
}
.col--dark .switch__surface-glare {
  background-image: radial-gradient(50% 50% at center,hsla(var(--hue),10%,45%,1),hsla(var(--hue),10%,45%,0));
}
.col--dark .switch__input {
  background-color: hsl(var(--hue),10%,20%);
}
.col--dark .switch__inner {
  background-color: hsl(var(--hue),10%,22%);
}
.col--dark .switch__inner-glare {
  background-image: radial-gradient(50% 50% at center,hsla(var(--hue),10%,45%,1),hsla(var(--hue),10%,45%,0));
}
.col--dark .switch__rocker-shadow {
  box-shadow: 0 0.125em 0.25em hsla(0,0%,0%,0.5);
}
.col--dark .switch__rocker-sides {
  background-color: hsl(var(--hue),10%,20%);
}
.col--dark .switch__rocker-sides-glare {
  background-image: linear-gradient(90deg,hsla(var(--hue),10%,35%,0),hsla(var(--hue),10%,35%,1),hsla(var(--hue),10%,35%,0));
}
.col--dark .switch__rocker {
  background-color: hsl(var(--hue),10%,20%);
}
.col--dark .switch__rocker-glare {
  background-image: linear-gradient(120deg,hsla(var(--hue),10%,25%,0) 25%,hsla(var(--hue),10%,25%,1) 50%,hsla(var(--hue),10%,25%,0) 75%);
}
.col--dark .switch__light {
  background-image: linear-gradient(-45deg,hsl(var(--hue),10%,30%) 30%,hsl(var(--hue),10%,50%));
}

/* “On” state */
.switch__input:checked ~ .switch__surface .switch__surface-glare {
  transform: translate(3em,0.125em);
}
.switch__input:checked ~ .switch__inner {
  transform: translate(-0.125em,0);
}
.switch__input:checked ~ .switch__inner .switch__inner-glare {
  transform: translate(0,-0.5em);
}
.switch__input:checked ~ .switch__rocker {
  transform: rotateY(20deg) translateZ(0.5em);
}
.switch__input:checked ~ .switch__rocker .switch__rocker-glare {
  transform: translateX(33%);
}
.switch__input:checked ~ .switch__rocker-sides {
  transform: rotateY(20deg) translateZ(0.5em);
}
.switch__input:checked ~ .switch__rocker-sides .switch__rocker-sides-glare {
  transform: translateX(-50%);
}
.switch__input:checked ~ .switch__light {
  transform: translate(-50%,-50%) rotateY(20deg) translateX(1.125em) translateZ(0.51em);
}
.switch__input:checked ~ .switch__light .switch__light-inner {
  opacity: 1;
}

/* Viewports beyond mobile */
@media (min-width: 768px) {
  main {
    flex-direction: row;
  }
}