<input type="checkbox" id="darkmode-toggle" />
<label for="darkmode-toggle">
  <svg version="1.1" class="sun" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" viewBox="0 0 496 496" style="enable-background:new 0 0 496 496;" xml:space="preserve">

    <rect x="152.994" y="58.921" transform="matrix(0.3827 0.9239 -0.9239 0.3827 168.6176 -118.5145)" width="40.001" height="16" />
    <rect x="46.9" y="164.979" transform="matrix(0.9239 0.3827 -0.3827 0.9239 71.29 -12.4346)" width="40.001" height="16" />
    <rect x="46.947" y="315.048" transform="matrix(0.9239 -0.3827 0.3827 0.9239 -118.531 50.2116)" width="40.001" height="16" />

    <rect x="164.966" y="409.112" transform="matrix(-0.9238 -0.3828 0.3828 -0.9238 168.4872 891.7491)" width="16" height="39.999" />

    <rect x="303.031" y="421.036" transform="matrix(-0.3827 -0.9239 0.9239 -0.3827 50.2758 891.6655)" width="40.001" height="16" />

    <rect x="409.088" y="315.018" transform="matrix(-0.9239 -0.3827 0.3827 -0.9239 701.898 785.6559)" width="40.001" height="16" />

    <rect x="409.054" y="165.011" transform="matrix(-0.9239 0.3827 -0.3827 -0.9239 891.6585 168.6574)" width="40.001" height="16" />
    <rect x="315.001" y="46.895" transform="matrix(0.9238 0.3828 -0.3828 0.9238 50.212 -118.5529)" width="16" height="39.999" />
    <path d="M248,88c-88.224,0-160,71.776-160,160s71.776,160,160,160s160-71.776,160-160S336.224,88,248,88z M248,392
        c-79.4,0-144-64.6-144-144s64.6-144,144-144s144,64.6,144,144S327.4,392,248,392z" />
    <rect x="240" width="16" height="72" />
    <rect x="62.097" y="90.096" transform="matrix(0.7071 0.7071 -0.7071 0.7071 98.0963 -40.6334)" width="71.999" height="16" />
    <rect y="240" width="72" height="16" />

    <rect x="90.091" y="361.915" transform="matrix(-0.7071 -0.7071 0.7071 -0.7071 -113.9157 748.643)" width="16" height="71.999" />
    <rect x="240" y="424" width="16" height="72" />

    <rect x="361.881" y="389.915" transform="matrix(-0.7071 -0.7071 0.7071 -0.7071 397.8562 960.6281)" width="71.999" height="16" />
    <rect x="424" y="240" width="72" height="16" />
    <rect x="389.911" y="62.091" transform="matrix(0.7071 0.7071 -0.7071 0.7071 185.9067 -252.6357)" width="16" height="71.999" />
  </svg>
  <svg version="1.1" class="moon" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" viewBox="0 0 49.739 49.739" style="enable-background:new 0 0 49.739 49.739;" xml:space="preserve">
    <path d="M25.068,48.889c-9.173,0-18.017-5.06-22.396-13.804C-3.373,23.008,1.164,8.467,13.003,1.979l2.061-1.129l-0.615,2.268
       c-1.479,5.459-0.899,11.25,1.633,16.306c2.75,5.493,7.476,9.587,13.305,11.526c5.831,1.939,12.065,1.492,17.559-1.258v0
       c0.25-0.125,0.492-0.258,0.734-0.391l2.061-1.13l-0.585,2.252c-1.863,6.873-6.577,12.639-12.933,15.822
       C32.639,48.039,28.825,48.888,25.068,48.889z M12.002,4.936c-9.413,6.428-12.756,18.837-7.54,29.253
       c5.678,11.34,19.522,15.945,30.864,10.268c5.154-2.582,9.136-7.012,11.181-12.357c-5.632,2.427-11.882,2.702-17.752,0.748
       c-6.337-2.108-11.473-6.557-14.463-12.528C11.899,15.541,11.11,10.16,12.002,4.936z" />
  </svg>
</label>

<div class="background"></div>

body {
  margin: 0;
  width: 100vw;
  height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

label {
  width: 500px;
  height: 200px;
  position: relative;
  display: block;
  background: #ebebeb;
  border-radius: 200px;
  box-shadow: inset 0px 5px 15px rgba(0, 0, 0, 0.4),
    inset 0px -5px 15px rgba(255, 255, 255, 0.4);
  cursor: pointer;
  transition: 0.3s;
  &:after {
    content: "";
    width: 180px;
    height: 180px;
    position: absolute;
    top: 10px;
    left: 10px;
    background: linear-gradient(180deg, #ffcc89, #d8860b);
    border-radius: 180px;
    box-shadow: 0px 5px 10px rgba(0, 0, 0, 0.2);
    transition: 0.3s;
  }
  svg {
    position: absolute;
    width: 120px;
    top: 40px;
    z-index: 100;
    &.sun {
      left: 40px;
      fill: #fff;
      transition: 0.3s;
    }
    &.moon {
      left: 340px;
      fill: #7e7e7e;
      transition: 0.3s;
    }
  }
}

input {
  width: 0;
  height: 0;
  visibility: hidden;
  &:checked + label {
    background: #242424;
    &:after {
      left: 490px;
      transform: translateX(-100%);
      background: linear-gradient(180deg, #777, #3a3a3a);
    }
    svg {
      &.sun {
        fill: #7e7e7e;
      }
      &.moon {
        fill: #fff;
      }
    }
    + .background {
      background: #242424;
    }
  }
  &:active:after {
    width: 260px;
  }
}

.background {
  width: 100vw;
  height: 100vh;
  background: #fff;
  z-index: -1;
  position: absolute;
  transition: 0.3s;
}

// Reference: https://redstapler.co/pure-css-minimal-dark-mode-toggle-button/