lbry.com/web/scss/_slider.scss

$checked-color: #006148;
$unchecked-color: #888;

.slider-checkbox {
  position: relative;

  input {
    width: 40px; height: 20px;
    top: 0; left: 0;

    background-color: red;
    cursor: pointer;
    margin: 1px 0 0 0;
    opacity: 0;
    position: absolute;
    z-index: 1;

    &:not(:checked) + .label {
      &::before {
        background-color: $unchecked-color;
        content: "\f00d";
        padding-left: 18px;
        text-align: center;
      }

      &::after {
        left: 1px;
      }
    }

    &:checked + .label {
      &::before {
        background-color: $checked-color;
        content: "\f00c";
        padding-right: 17px;
        text-align: center;
      }

      &::after {
        left: 21px;
      }
    }
  }

  .label {
    padding-left: 40px;
    position: relative;

    &::before,
    &::after {
      border-radius: 0;
      position: absolute;
      transition: background-color 0.3s, left 0.3s;
    }

    &::before {
      width: 40px; height: 20px;
      top: 0; left: 0;

      box-sizing: border-box;
      color: white;
      font-family: 'FontAwesome', sans-serif;
      font-size: 12px;
      line-height: 20px;
    }

    &::after {
      width: 18px; height: 18px;

      background-color: white;
      content: "";
      top: 1px;
    }
  }
}